I've been working as a IT developer for years and have also helped run a computer store for my friend fixing all types of computers.
Stay away from: HP(conpaq), Dell, <<-high repairs
Toshiba was great years ago, but they changed their strategy to go for high volume sales and they stink now.
Consider: Gateway(same as Acer, Emachinces) << best bang for your dollars and are good for all needs of a high school kids. Maybe not for hard core gamers but can work.
Lenovo(old IBM): These are rock solid but are not flashy. May not work for a high school.
something good under $400 will be hard to get and might have to be a HP.
Consider these one
Or this site for Lenovo Friends and Familys.
Password: IBMEPP (all CAPS)
Look for Ideapad.