Paying Child Support For 18 Year Old Not In High School

My husband's 18 year old daughter is enrolled in independent study (California), but she has not been attending. She has only been twice in 7 weeks. When she does go, she doesn't take the tests to get the credits and will not be graduating.

Are we required to continue paying child support (currently going back to court) for an adult who doesn't actually go to school even if she is enrolled? She wants to enroll in summer school and the fall semester; however, my suspicion is that it is just a way to get more money until she is 19. I don't see the past behavior changing and suddenly becoming responsible about school.