I have a similar situation - My middle DD (almost 6 years old and in kindergarten) is a level 4 and practices 9.5 hours a week, all on school days. She gets out of school at 3:30, and we drive straight to the gym for practice at 4.
Things I've done to help with our busy schedule:
-Make sure I have a healthy, filling snack and drink ready in the car for on the way to practice.
-Lots of crock pot meals that are ready to eat right when we get home from practice at 7:30.
-Earlier bedtime (by 30 minutes) on non-gym nights to catch up on sleep.
-Limit other activities. She's had to opt out of joining Girl Scouts, soccer, dance, etc., but I think it's worth it. Gymnastics has been great for developing her fitness and self-esteem, and she's having so much fun being on the team.
-I've talked to her teacher about her practice schedule, and asked that the teacher let me know if DD ever seems overtired or unfocused during the school day.
Sometimes my DD whines in the car on the way to gym, or cries afterwards (usually signs that she is either tired or hungry) - but she is always happy during practice. If she were to start crying during practice I would shorten her hours or take an occasional day off to give her some down time.
It seems like your gym has a lot of hours for pre-team. Does your gym start competition at level 5?