what are the a-g classes? Do you have to take certain classes to be eligible to apply for the UC system? Are these necessary classes?
You need to meet the minimum a-g courses, however to be a competitive applicant you need to go above and beyond the minimum. If you are a CA resident, your HS curriculum should cover all the requirements. If you are OOS, then you need to make sure you meet the required courses especially the Visual/Performing arts requirement.
Also if you are OOS then realize you will be full pay. Make sure your parents can afford it.