I took 10 hours this summer (3 classes) and it was a little bit crazy! My school's summer terms are really weird - I took 2 courses over the 11 week term, and one in an 8 week term that ended before the longer term. So for most of the summer I was taking all 3 classes, and it was a lot. The classes weren't terribly difficult, but they were all very time consuming. The worst part was when I had 2 or 3 exams or major assignments at the same time, there would be a day or two where I couldn't give DS as much time and attention as usual, and I felt really guilty about that. Fortunately, he's a pretty "go with the flow" kid and did fine. If you use childcare while you are in class/studying, or if your DH, other family members and/or friends are able and willing to spend some time with your DC when you have a lot of schoolwork, that would really help.