Macs definitely have less downtime, shorter startup time and better battery life than windows machines. Windows has certainly gotten better over the last few years, but 5 years ago it would be taking a minute or two for windows to wake up and log in between each class. Mac is pretty much instant (Chromebooks are fast too). Before you say that a minute isn't much, consider that you have 25 teenagers in the classroom, with a minute of boredom.

Also, build quality, effective lack of malware and other system problems mean students (and teachers) don't have to deal with broken computers nearly as often.

It's only the last couple of years that windows has come close, and for hardware the compares in terms of durability, you'll be paying as much as Apple anyway (which schools are hesitant to do as they are underfunded)

I speak from years of experience as a teacher and IT manager, and as an apple hater.