^With a green card you’re treated exactly like a citizen, which is why it’s so very important for an international who’s finishing the process to apply when s/he can do so as a permanent resident.
Yes for the purpose of admissions all students enrolled in US high schools are treated like domestic applicants. They’re compared to students enrolled in similar high schools.
However, for the purpose of financial aid, they are NOT considered like residents of California, which means they must pay 55K+ and have NO financial aid, not even loans. Whereas, if they are considered permanent residents, they pay instate fees and can benefit both from state grants and federal aid. The difference is wort 30-45K a year.