I took the PE Environmental and just passed. I used School of PE. It was great for me. I did the weeknight option so I had class from 7-10 pm Monday through Thursday for 5 weeks. I think all of the topics were covered very well, but of course you will need to have the right reference material. You'll have tons of practice problems at your disposal. Check out the Environmental page here, you'll find a plethora of resources and amazing advice.