hmmm
I don't think starting classes right now would be the best thing.
Your baby is very young, and should not at any time be on the ground,grass or any other place another dog has been. She's way too young to have had all her Parvo shots. Parvo is something you have to take very seriously. Once a furbaby gets it, many don't make it. I'm surprized your Vet didn't warn you about this. And I'm very surprized the classes are letting you in with such a young pup.
Good Luck To You