Yes, and to expand just a little on what O8Dad has said, there are at least three routes in to the UCs. One is the ELC ("Eligibility in the Local Context"). For the top 3% of your HS, this means an AUTOMATIC admit to the UCs (it does not however mean an automatic into the UC of your choice, but you will get a letter in the fall of your senior year from the UC(s) that you are in to based upon this, generally the three-four impacted UCs do not do this (Cal, LA, SD, and now maybe even SB). You will know if you are close to the top 3% by the spring of your JR year, because your HS must get your signed permission to release your grades to the UCs, and that is when those HS letters come out (but they do slightly over-include because generally a HS does not calculate its GPAs like the UCs do, so you may just miss the cutoff in the fall).
Then there is the weighted GPA that 08 mentions - top 12% I think fits into this grouping, which means you qualify, but if the numbers of applicants are to high, you may not make it in. Then there are the athletes and others - and yes, athletes do have to make an academic criteria, albeit lower than non-athletes.
For admission purposes, almost every college/university ranks grades #1, then standardized test scores #2, then it can start to vary (like community service, letters of rec., etc.)