I would have him look at some of the Western Undergraduate Exchange schools (WUE). While academic quality of in-state CA schools is hard to beat, if he is determined to go OOS, he might quality for WUE tuition at various schools in the Northwest. If he likes outdoor recreation, maybe look to Western Washington (fantastic mid-sized school north of Seattle), Washington State, or the WUE publics in Idaho, Montana, or Wyoming. They are not T-25s but there are probably some that he might like.
There are some WUE options in Colorado, too, but Boulder is not among them, AFAIK.
Good luck!