retake SAT to improve essay score?

My son scored 1500 on the SAT (math: 720 EBRW: 780) but only a 16 on the essay. We live in CA and he would like to apply to the UCs, which require the essay. Is it worth him retaking it? Thank you!

Yes. If schools that you are applying to require the essay, the score of the essay matters. But in general for other schools that don’t require the SAT portion (which is tons of highly selective schools), that is irrelevant.