Also, as was mentioned in a previous thread, if his grades put him in the top 9% of California seniors, then he is pretty-much guaranteed admissions to UC Merced even without applying – but not necessarily in his first choice major, if that major is impacted. He could also apply to UC Merced directly in order to get his first choice major.
Edited to add a relevant link:
Statewide guarantee | UC Admissions (universityofcalifornia.edu)](Statewide guarantee | UC Admissions)