I think it's meant to reinforce both
her inherent smartliness and the way city schools are apparently ahead of rural ones. Which might have been true years ago, but with the extent that high schoolers get tested these days? Everyone in the state is going to have gone at essentially the same pace. Washington as a whole would have to be behind Arizona. I think it would have been better to have something like Forks doing Earth Science and then Bio, while Phoenix did Bio and then Earth Science - it would have gotten the point across that she was in a ~difficult situation~ without the unfortunate implications.