It's fine to skip pre-algebra as it's more of a geometry primer.
As mentioned above, what is taught each year can vary a lot between state to state and school district to school district. My ds' pre-algebra class was not a geometry primer at all, and actually contained quite a bit of algebra - so if he'd totally skipped it he would have had quite a bit of making up to do on his own. He did skip the 6th grade math level that goes before pre-algebra in our school district, but he'd also done quite a bit of online math courses at home on his own.
polarbear
