What paper has to do that a screen does not
A screen marks a mistake. A worksheet has to wait to be marked.
Every puzzle app on the internet tells a child immediately when a digit is wrong. On paper nothing does, and the gap between making a mistake and finding out is where a worksheet either works in a classroom or wastes twenty minutes of it. On this site that gap has been measured rather than guessed.
How long a Sudoku waits before it tells you
Take a medium Sudoku and write one wrong digit in an empty square, choosing a digit that does not already appear in that row, column, or box, so it is a mistake nobody would spot by looking. Then carry on solving normally, filling in only the squares where exactly one digit can possibly go. The question is how many squares you get to fill before the grid becomes impossible.
- Caught at once
- A few squares of wasted work
- Most of the remaining sheet
Only 4.3 per cent of wrong entries are caught immediately. In a further 13.1 per cent the straightforward deductions simply run out without the grid ever contradicting itself, which is the worst outcome of all: the sheet has not objected, it has just stopped giving anything away, and from the solver's chair that is indistinguishable from a hard puzzle.
A child working in pen has, on average, another 9 squares of honest effort ahead of them before the sheet admits that the last ten minutes were wasted.
What this means for handing sheets out
Send pencils and rubbers with the grid-deduction puzzles, and mean it. This is not tidiness advice: a wrong digit in pen makes the sheet unrecoverable, and the child who has to start again is usually the one who was already finding it hard. Word searches and mazes have no such problem and can go out in pen.
Which sheets correct the child, and which need you
The measurement above is the extreme case. The builders are spread across a wide range, and the difference is structural rather than a matter of difficulty: some of these puzzles carry their own answer key on the page, and some cannot.
| Puzzle | When a mistake shows up | Why | Pen or pencil |
|---|---|---|---|
| Word Search | Immediately, and for free | The word list beside the grid is the answer key. A word you cannot find is not crossed off, and a word you think you found either spells the word or it does not. | Safe in pen |
| Mazes | Within a few squares | On Easy there are no loops at all, so every wrong turn ends in a dead end that hands the pencil back. The maze corrects the child without an adult in the room. | Safe in pen |
| Word Scramble | At once with a word bank, eventually without | With the word bank on, a wrong answer is a word that is not on the list. With it off, a plausible-looking wrong answer can survive to the end of the sheet. | Safe with the word bank on |
| Cryptograms | Within a word or two | A wrong letter spreads to every cell holding that cipher letter and starts producing unpronounceable words almost at once, which is the sheet objecting in the clearest way any of these do. | Risky: the whole sheet shares one alphabet |
| Futoshiki | Only when a line runs out of numbers | Sheets are proved solvable by deduction before printing, so a solver who never guesses never goes wrong. A solver who does guess gets no warning until a row cannot be completed. | Pencil |
| KenKen | When a cage will not make its total | Arithmetic gives slightly earlier warning than plain Sudoku, because a cage that cannot reach its target is visible without looking at the rest of the grid. | Pencil |
| Kakuro | When a run will not make its total | Same shape of feedback as KenKen, over longer runs, so the warning arrives later and further from the mistake that caused it. | Pencil |
| Killer Sudoku | Later than anything else here | No digit is given, so there is nothing to check a wrong entry against until a cage total or a line refuses to work. It also has the best built-in check of the four grid puzzles once a cage is full: the digits either make the printed total or they do not. | Pencil, firmly |
| Sudoku | On average not for another few squares | Measured below: after one wrong but legal digit, a solver can fill a median of 9 more squares, and sometimes as many as 40, before anything on the sheet objects. | Pencil, and this is the one that matters |
The Sudoku row is measured. The other seven are structural properties of each puzzle rather than measured figures, and are described as such rather than dressed up with numbers.
The word search is worth singling out, because it is the only puzzle on the site that a solver cannot get wrong, only leave unfinished. The word list printed beside the grid is the answer key: a word is either there in a straight line or it is not, and no amount of wrong work makes the rest of the sheet impossible. That is why it is the safest thing to leave with a cover teacher, and also why it teaches the least.
Can a class of 30 each have a different sheet?
Differentiation usually means different difficulties. The other question, and the one that catches people out, is whether thirty children can have thirty different puzzles at the same difficulty, so that the answers cannot simply travel along the row. For 8 of the 10 builders the answer is yes at any setting. For two of them it depends on the setting, and the builder does not currently warn you.
| Builder | 30 different sheets? | Detail |
|---|---|---|
| Sudoku | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| KenKen | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Kakuro | Depends on the setting | 8 of the 18 size and difficulty combinations hold fewer than 30 puzzles. The smallest holds 10, so a class that size cannot all have a different 10x10 hard sheet. |
| Futoshiki | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Word Search | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Word Scramble | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Cryptograms | Not from one category | 16 quotations per category, so a class of 30 needs the mixed setting, which draws on all 96. |
| Mazes | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Killer Sudoku | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
| Logic Puzzles | Yes, at any setting | Each pack is generated on request, so five packs of six give thirty different sheets at the same difficulty. |
Counted at build time from the shipped Kakuro bank files and the cryptogram quote data. The all-puzzles index looks at the same figures from a different angle: which builders are finite and why.
Print settings that save real money
- Ink saving thins the grid lines rather than greying the whole sheet, so a class set costs noticeably less without becoming hard to read. It is the single most useful classroom option here.
- Two puzzles per page halves the paper on every builder that offers it, which is all but the word search. A word search needs the whole page for its grid and list.
- Answer keys can be printed four to a page on some builders, so a set of keys for the teacher is one sheet rather than six.
- Large print is not only for sight. A younger child writing with a fat pencil needs the square to be bigger, which is the same setting for a different reason.
- Set the worksheet title to the topic or the class name. It is the difference between a pile of sheets and a pile of sheets you can sort.
Using your own word list
Two builders take a pasted list of your own words: the word search and the word scramble. That turns a generic puzzle into this week's spellings, this term's topic vocabulary, or the names of everything in a science unit, and it is the strongest classroom feature on the site.
Both builders check the list before they use it and tell you what they dropped. A word containing another word on the same list is removed, because the grid would hold two valid answers. Words of three letters are refused on the scramble, because TAR, RAT, and ART all come from the same letters and a child can be right and marked wrong. Two words with identical letters cannot share a scramble sheet for the same reason.
The 14 ready-made lists carry a reading band each, so you can pick by age rather than by topic when that matters more.
What to print for what lesson
| If you need | Settings to start from | Why that one | |
|---|---|---|---|
| Five minutes at the start of a lesson, whole class, same sheet | Word Search | 12x12, Medium, 2 per page | Two on a page halves the paper, and nobody needs the rules explaining. |
| A cover lesson left for somebody else to run | Mazes | 6 mazes, mixed sizes, solution keys on | No subject knowledge needed to hand out, and the keys mean the cover teacher can mark it. |
| Vocabulary or spelling from a topic list you already have | Word Scramble | Custom word list, Easy or Medium, word bank on | Paste your list in and the sheet is your list, not a generic one. |
| The same topic list, but a gentler task | Word Search | Custom word list, Easy | The same words, but recognising rather than spelling them. |
| Mental arithmetic practice that does not look like a worksheet of sums | KenKen | 4x4 or 5x5, addition only to start | Every clue is a small calculation, and the grid rule stops guessing. |
| Stretch for the two or three who finish everything early | Kakuro | 9x9 or larger, Hard | The longest sitting on the site, and it needs no new rules taught. |
| Mental addition practice for older students, disguised as a puzzle | Killer Sudoku | Easy or Medium, one per page | Every cage is a small addition problem, and the grid rules stop anyone guessing their way through. |
| A reasoning lesson where the method is the point | Futoshiki | 5x5, Medium, one per page | The only builder that proves each sheet is reachable by deduction, so "I guessed" is never the right answer. |
| Form time, an end of term, or a reading-adjacent filler | Cryptograms | Easy, short quotes, working strip on | Finishes with a sentence worth reading out, which most puzzle sheets do not. |
What this hub does not do, and should say so
There is no curriculum alignment here. Nothing on this site is mapped to a national curriculum, a year group, or a set of learning objectives, and the age guidance that does exist comes from what a sheet requires rather than from classroom observation. A puzzle that practises addition is not the same thing as a resource that evidences it, and this site does the first.
There is also no way to build one PDF containing three difficulties at once, which is what differentiation in a single class actually needs. Today that means three downloads and three print runs. It is the most requested-shaped gap on this page and it is a builder change rather than a content one.
Two planned builders are aimed squarely at this hub. Neither exists yet, so neither is a link.
Printable Binary Puzzles
Only noughts and ones, with three short rules. The natural entry point for anyone who finds Sudoku heavy going.
Not built yetPrintable Hidden Message Puzzles
A word search whose leftover letters spell a phrase. An upgrade to the word search engine rather than a new one, targeting a distinct set of searches.
Not built yetPrintable Math Puzzles
Number pyramids, magic squares, and target-number sheets, graded by age band rather than by puzzle type.
Not built yetPrintable Picture Sudoku
Sudoku with symbols instead of digits, for children who can match shapes before they can read numbers.
Not built yetPermission, and who checks these
Print Puzzles is part of the Hamilton Digital Media Limited puzzle network, and these pages are written and reviewed by Brian Hamilton and Karan Hamilton. The terms of use give broad permission to print, copy, and hand out these worksheets and answer keys for classroom, tutoring, library, club, and community use, with no attribution required and no licence to buy. Every builder is checked in bulk before its page goes live, and what that involves is set out on how we make puzzle packs. If a sheet or a key is wrong, the contact page is the fastest route to getting it fixed.