What am I?

I use to have bells every hour or so,

About 30 to 40 kids in a room,

Less ground to cover,

And less parking space.

But what stayed the same:

Is the adults who teach,

The students who learn,

And not enough parking spaces for everyone.

Now I have no bells,

Parking all around me,

A parking structure,

Beautiful trees and perfect grass,

And so much more students learning in me.

What am I?