Utah has some of the largest class sizes in terms of student/teacher ratio in the nation; California has one of the smallest.
This is not surprising. There is very little evidence that "smaller class size" improves student performance. Small class size mostly helps poor students in low grades, and even then, much of the benefit is because of a reduction in distracting noise. Noise absorbing insulation is far cheaper than hiring more teachers, and may do almost as much good.
Utah ranks twice as high in SAT scores by students than California.
SAT scores are a terrible metric to compare schools. SATs are specifically designed to measure raw ability, and to exclude, as much as reasonably possible, the benefits of education. According to this chart the average American SAT score in 2013 was 1498, while California's was 1505 and Utah's was 1694. BUT WAIT: in California, 57% of high school students took the SAT, while in Utah just 6% took it. So the top 6% of Utah are better than the top 57% of California students on a test that is specifically designed to NOT measure the quality of their education. I am not sure what to conclude from that.