Maybe I'm misunderstanding ...
You want your phone to access the internet through your school's (probably filtered) network instead of using your data plan?
That's what I think when you say reverse tethering. Unless you are referring to bluetooth tethering where you would tether your laptop to your phone using bluetooth, and then go out to the internet through your phone data plan.
Bluetooth tethering is possible, now whether your school's laptop security settings will allow you to tether is another story entirely...