My D2 took a couple summer courses 2 years ago. One is online (health) and the other one is outdoors (PE). Both are only ~3 weeks long. For the online course, the student can work on his/her own pace as long as finishing up within the 3-4 weeks time frame allowed. So it fits family vacation schedule easily if the trip is not more than a week long. She took those summer courses because of schedule conflict (school offer less classes after school district cutting budget) and we do not want her to leave those electives to junior/senior year when she should take other advanced level classes. The bad part is we need to pay for the summer courses for the trouble created by the school district at ~$350 per course.