Just to share part of the email reply I received from AoPS w.r.t. international students.
"Our classes are open to international students, though for many, the time difference is a difficulty. Students who use the books but not the classes miss the following:
1) The opportunity to work with AoPS instructors and ask them questions about the material,
2) The opportunity to receive feedback on their work, and
3) The opportunity to work with many other outstanding math students.
This said, there are a great many students who use our books without the classes, as the books are designed specifically for high-performing students who are pursuing independent study."
