Child Support after child turns18 years of age, no diploma and not enrolled in traditional high school?

My daughter turns 18 next month. She has not graduated High School but she does not attend a regular school. She is not homeschooled but she is enrolled in a school through Renton school district that is online. She only sees a teacher one day a week for about 2 hours to turn in work and receive new work and some help.
My ex and I no longer go through the courts but I want to know if it did, would support have to continue to be paid until she finishes her courses or turns 19? Her teacher is now saying she may have to go another year! If she was in traditional school that would make it her 6th year in high school.