For FLVS, you will pay the same through PEP as if you were enrolling in their global program as a paying student.
For public school classes, it varies from district to district.... You would have to call the school district.
Please note that there will be a cost for public school classes if you are a PEP student. Regular home education students don't get any additional funding or access to the tax dollars that go to the schools, so they can enroll without cost for classes at a public school. The school receives funding through the Department of Education for those students.
However, PEP students are already receiving funding from the PEP scholarship. This is why there is a cost for these classes for PEP students--if you didn't have to pay, it would be double-dipping. (In other words, your students would be getting an unfair advantage over other students.) (For more info on this "double-dipping" concept and why it's set up this way, see our FAQ post here.)
Update: Please also see this September 7, 2023 update about classes at public schools.
My district doesn't seem to have a clue. I am happy to pay, but they don't know how to charge me :(