Why the sheet must print at 100% (and never “fit to page”)
Your printer's “fit to page” option shrinks the sheet by a few millimetres, and that is what stops the grading from lining up with the paper. How to turn it off, and how to check with a ruler.
If you printed the answer sheet and the grader cannot read it, the likely culprit is not the camera or the classroom light: it is the printer having shrunk the paper without telling you.
What “fit to page” actually does
Almost every print dialog ships with an option turned on called “fit to page”, “scale to fit”, or “shrink oversized pages”. It exists for a good reason: no printer prints all the way to the edge of the paper, so the software shrinks the document by 3% to 5% to keep anything from being cut off.
For ordinary text that is invisible. For the answer sheet it is not: the grader finds the four corner squares and, from the distance between them, works out where each bubble should be. If the whole sheet shrank, every distance changed at once — and the bubbles stop landing where the arithmetic expects them.
The sheet does not need to be perfectly square to the camera: the grader corrects tilt and perspective on its own. What it cannot correct is paper printed at the wrong size.
How to turn it off, in what you probably use
- Chrome or Edge: in the print dialog open “More settings” and set “Scale” to “Custom: 100”. Do not leave it on “Fit to printable area”.
- Safari on a Mac: uncheck “Scale to fit paper size”, or set the scale to 100%.
- Acrobat Reader: under “Page sizing and handling”, pick “Actual size”. Never “Fit”.
- Check the paper size too: A4, not Letter. Swapping one for the other changes the sheet by nearly a centimetre.
The ruler check, once
The sheet carries a scale-check mark: a segment with its length printed beside it. Take an ordinary ruler and measure that segment on the printed sheet. If it reads 100 mm, the print came out at the right size and you never need to measure again on that printer.
If it reads 96 or 97 mm, some scaling option is still on. Go back to the print dialog, fix the scale, and print again. One sheet is worth spending on this: the error repeats on every test printed that way.
Two other things that get in the way
- Draft or eco mode: the ink comes out weak and the corner squares end up light grey. Print in normal black.
- Coloured or very dark recycled paper: the contrast between a filled bubble and the background is exactly what the grader measures. Plain white paper works best, and it is the cheapest.
Once the printer is set, you stop thinking about it. It is a thirty-second check that removes the biggest single cause of an unreadable sheet.