I want to have a different price when people order 5 or more. I cannot determine how to do that.

I want the form to allow people to pay $25 for one class or $20 per class if they order 5 or more. 

Enable special pricing so you can define custom pricing.

To do that, edit the quantity option in your product field.

Then enable special pricing and define the custom price for 5 quantity and over.

Example:

5x20 = 100

6x20 = 120

Hope this helps!