This is why I am reluctant to just jump to the simplest conclusion.

Some classes will have to be present at some schools because the students going there require it (individualized help with reading, etc) more than other populations. If the non-native English speaking population is higher, then more ESL classes. Responding to specific needs could mean more teachers needed to supply those types of courses and so they have fewer other types of courses. On the other end, in some school districts, you have AP classes offered within the district but not all of them at the same school (and its up to you to transport yourself between schools).