Thirty students, thirty sheets, 1,440 pieces
A class set is not thirty times one puzzle. It is thirty puzzles that will end up in the same box, and the boring part — sorting them back out — is what decides whether you do this again next term.
The material list
Thirty students, one sheet each, front and back. Duplexed, that is thirty sheets of card and sixty printed sides. Everything below is that, plus what it takes to keep the pieces apart.
| Item | Quantity | Why that number |
|---|---|---|
| A4 200 gsm card | 35 sheets | 30 for the class, 5 for jams and reprints; a 50-sheet pack covers one and a half classes |
| Printed sides | 60 | Front and numbered back, duplexed on the long edge |
| Pieces produced | 1,440 | 30 sheets × 48 pieces at 6 × 8 |
| A5 envelopes | 30 | One per student, named on the outside |
| Scissors | 15 pairs | Two students to a pair, cutting in parallel |
200 gsm is the weight that feeds in most inkjets and still holds a tab. At 80 gsm the pieces delaminate at the tabs within a few solves — see the paper guide for the weight chart.
The problem with identical sheets
Here is the detail almost nobody plans for. The cut pattern is generated from the settings — grid, cut style, tab size, jitter — and those settings come from the sheet you configured. Print thirty sheets with the same settings and you get thirty identical sheets, down to the shape of every tab.
That is normally a feature: it means a reprint matches the sheet you already cut. In a classroom it means a piece from Amara’s puzzle fits Priya’s puzzle exactly. Once two sets are on the same table, no shape, no colour and no edge tells them apart. You are left sorting 96 identical pieces into two piles of 48 by eye, and you will get it wrong.
The same applies to the picture, if the class uses one shared photo. Different photos make a heap sortable by image; identical photos do not. Either way, the fix is the same two moves below.
Fix one: three different grids
Pieces from different grids are not merely different — they are physically incompatible. A 5 × 4 sheet on A4 has 38.0 mm cells; a 6 × 8 sheet has 31.7 mm. A 38 mm tab cannot seat in a 31.7 mm socket, so mixed pieces sort themselves by refusing to fit.
| Group | Grid | Pieces | Cell | Cut per sheet |
|---|---|---|---|---|
| Table 1 | 5 × 4 | 20 | 38.0 mm | 2.51 m |
| Table 2 | 6 × 8 | 48 | 31.7 mm | 4.90 m |
| Table 3 | 8 × 11 | 88 | 23.5 mm | 6.62 m |
Ten students per group, and the younger the group the lower the grid. Ten sheets at 8 × 11 is 66 m of cutting, so put the highest count with the students who can be trusted with scissors for an hour.
Fix two: print the numbered back
The back sheet prints the same cut pattern with a position number in every cell, running left to right and top to bottom. It is the only thing that survives a total mix-up: read the number, and you know both where the piece goes and which grid it belongs to, because 88 is not a number a 20-piece sheet can produce.
Two settings make it work. Duplex has to flip on the long edge, and the back sheet is mirrored about the grid centre before it is printed so that the flip lands the numbers behind the right pieces. The numbered backs page has the table of printer settings and what happens when the flip is wrong.
What the cutting actually costs
Measured per sheet and multiplied out, because a class set is the one case where the total matters:
| Grid | Pieces per sheet | Per sheet | 30 sheets |
|---|---|---|---|
| 4 × 3 | 12 | 1.92 m | 58 m |
| 5 × 4 | 20 | 2.51 m | 75 m |
| 6 × 8 | 48 | 4.90 m | 147 m |
| 8 × 11 | 88 | 6.62 m | 199 m |
Straight cuts are about 30% shorter: a square grid at 6 × 8 is 3.48 m per sheet, or 104 m for the class. If an adult is doing the cutting rather than the students, that is the difference between one evening and half of one.
There is no way around this number, only a choice about who spends it. Cutting thirty sheets of 48 tabs is 147 metres of scissors work; ten students cutting their own sheet is 4.9 metres each, which is an activity in itself and teaches the part that matters — that the sheet has to be printed at 100% or nothing fits. Check the first one against the 100 mm bar before the other twenty-nine go through.
Handing out and packing away
Give every student an A5 envelope at the start and make the rule that pieces go in the envelope, not on the table, the moment a set is finished. A named envelope is a complete solution to the problem of half-finished puzzles at break.
For a set that will be reused, laminate after cutting rather than before — film over the sheet bridges the cut lines and your knife scores the plastic while the paper stays intact. Cut pieces run through a pouch come out wipe-clean and about 0.2 mm thicker, which makes tabs seat more tightly. It is slow work, and it is the difference between a set that lasts a term and one that lasts a week.
Print one sheet before you print thirty
Start at 20 pieces, check the 100 mm bar, then move the class up a grid if the pieces cut cleanly.