Heya!
I use a bit of rubbing alcohol to clean the print bed if my prints aren’t sticking. It helps ensure that there is no water or any other moisture on the build plate and usually works 
Regarding school glue sticks:
The glue has to be PVA glue, and to my knowledge, not all glue sticks contain large amounts of PVA (I’m no chemist or anything, but I believe PVA is a part of glue and is not the entire stick? I am probably wrong.)
Also depending on which material you are printing with, turning up the temperature on the build plate may be the solution. With the PLA’s I’ve printed, I’ve been unable to get them to adhere to the build plate without heating it. Usually heating the build plate to 50-60 C is sufficient with PLA. Any more and you may encounter warping as PLA’s glass temperature is just above 60 C or so. Don’t make the build plate too hot as it may not allow the filament to actually settle.
Something else you can do:
Print with a brim. It helps with PETG, PLA and ABS. Rafts even work with PLA quite well, however, they are rarely needed.
Hope that helps
-Greg