UC Admissons: Isn't That Special?

I see that on "all but three" UC campuses the mean GPA for next year's entering class is above 4.0. Is this not a remarkable result in a school whose public primary and secondary schools are regularly described as functioning 'way below par? I can offer several possible explanations:

• We take in a lot of out-of-state students.

• It's a two-peak distribution; a small but intense core of high achievers and a great unwashed mass of slackers.

• High school grades are a joke.

Re: the third point, I recall my friend Eliot telling me some years ago that the way to get an A at Palookaville high was to demand it.