Thanks for the links. This is because of my districts interpretation of a 2012 CA law that stating.

"AB 1575 reaffirms that students may not be charged fees to participate in any activity that is “educational in character,” though it does allow schools and districts to request voluntary donations to maintain programs and services."

My district is taking literally to mean they can't charge for summer school if the student is getting H.S. credit. Teachers can't ask students to purchase books during the school year or for summer reading. Honestly I don't mind that the student can read any book they really want this way. I just wish the teacher recommended list had been better.