I have been to Barnett's and it was a great experience.
There is a bicycle mechanic certification called the B.S.E. It stands for Bicycle Standard of Excellence. Kind like A.S.E. for automobiles. I took the test and received the certification. I went to Barnett's for the test since I had been there before but I think that there are other places that you can take it at.
I think you will appreciate any bike mechanic school that you got to. Good luck and enjoy.