Here are the answers to the AB test. Make sure you actually grade them.
https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_calculus_ab_sg.pdf
Here are the answers to the BC test:
http://media.collegeboard.com/digitalServices/pdf/ap/ap14_calc_bc_scoring%20guidelines.pdf
https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_calculus_ab_sg.pdf
Here are the answers to the BC test:
http://media.collegeboard.com/digitalServices/pdf/ap/ap14_calc_bc_scoring%20guidelines.pdf