Umut:
A self-printed projection print scale wouldn't work, unless you replaced all the numbers on it with letter codes, and then used up a whole bunch of paper to develop your own calibration table for it.
The product is/was recently sold under the Delta brand - perhaps you can find one in a retail source you can access.
I have a simple enlarging meter - an old Ilford EM-10 - which gives a bit of help. Basically, I use it to adjust the aperture on the enlarging lens to get the light intensity at the baseboard to a standard level with an empty carrier in the enlarger, then swap that carrier with the one holding the negative, check that the focus is still good, and then make my first test strip.
Basically, all I do with the EM-10 is get things to a place where the first test strip will likely tell me most of what I need. Sometimes it tells me all I need.
I generally only need to use the EM-10 at the beginning of a session, or when I'm changing lenses and film formats. I'd probably need it even less if I had a permanent darkroom setup.
One problem with enlarging meters is that you need to turn out all other lights in the darkroom - including safelights - in order for them to do their job right. That works in an individual darkroom, but can be difficult to arrange in a shared school darkroom.