Manny,
After you get the track and jumps built, you need to compact the dirt or the trucks will tear it up fast
Maybe if your school has an Ag department they might have a water filled type roller, other wise you could rent a compactor for like $50 at the equipment rental places. The Rollers work ok, just a lot of labor.
Also you need to 1- water it down, 2-let soak in, 3-compact, 4-repeat step 1, etc and etc until it’s somewhat hard packed.

Good luck