Yes, it looks like you would qualify for overtime. Anytime you teach more than 22 periods a week, you should be paid extra for any overage. I know in my contract, it is 20k for a class over the 22 during school hours, like after school classes or teacher classes, and 30k for any class outside of school hours, like weekend or evening classes.
If you are not scheduled for 22 classes, they can supplement your schedule with other classes, like morning or afternoon ones, up until the 22 class cut off without having to pay you extra.
Extra pay is done by the classes or periods you teach, not necessarily the extra time you are physically at school. If your class count is over 22, you should be getting extra pay. Be sure to confirm this with you school and look for it in your bank account. I know that my school pays my salary and afternoon class pay at different times in separate deposits.