Cartesian graph paper with axes, A3
Numbered axes through the center of an A3 sheet, which is the size a plot needs to be read across a room.
Opens with these settings already loaded. Change anything you like, then download as PDF, PNG or SVG.
A3 is for plots other people have to see
An A4 plot is for the person who drew it. A3 is what you pin up, project alongside, or work on as a group. At 5 mm spacing an A3 sheet gives roughly 56 squares across and 79 down, so you can plot a substantial range and still have each square visible from a few feet away. For classroom demonstration that legibility is the entire requirement.
Numbered axes remove a whole class of error
Counting squares out from the origin every time is where mistakes creep in, especially on a fine grid where being one square out is easy and invisible. Printed numbers on both axes remove that step and make the finished plot readable by someone who was not there when it was drawn. On a sheet this size, where the plot is likely to be shown rather than filed, that matters more than usual.
Pick the scale before the first point
Decide your units per square from the range of the data, not from the size of the paper, and write the scale on the axis. One unit per square is easiest to read, two and five are fine, and three or seven will make every subsequent reading an arithmetic problem. If your range does not fit at a sensible scale, that is a signal to use a logarithmic axis rather than to cram.
Printing it accurately
This only measures correctly if your printer doesn't rescale the page. In the print dialog set Scale: 100%, not "Fit to page" or "Shrink oversized pages". If you're not sure it worked, print the calibration page, measure the ruler on it with a real ruler, and it will tell you exactly what your printer is doing to the page.