RPi is pretty much the cheapest way to get a brand new, standardized device into the hands of each of 200 students, then give the same curriculum to each student that will work the same, with predictable errors the teacher is going to be more ready to troubleshoot, instead of trying to figure out why some kid's PC segfaults because of an error on a Broadcom device that was only available on devices manufactured in May of 2014 (but sold in September of 2017, the ones manufactured 05/2014 but sold before 9/2017 are perfectly fine) when he tries to use any function using sin in Python (but the libc one works just fine).

Schools have historically paid a premium for this, like the Basic Stamp, which was really just a PIC microcontroller preflashed with some other stuff on the PCB to help it run, and sold at a crazy markup, but was well integrated into a standard curriculum that gave every student the same starting point and something that a teacher could easily help hundreds of students with. It's also kind of why Arduino became so popular -- did the same thing, but a fraction of the cost.

I used to work for a company that sold pi kits for schools, you could let 7-9 year olds try stuff that teachers and parents would not let them do to a laptop. Totally breaking a computer and fixing it again is a great experience, but not one you want to have on your primary machine