Battling with parents

I am a cheerleading coach of 9-10 year old girls. There are 35 girls on my squad. I have recently had complaints from the parents that I'm working the girls to hard. The parents are arguing that 25 jumping jacks is too much for their children to do. Also, they argue that when the girls break safety rules while stunting, they shouldn't be disciplined in any way. My policy is that if you break a safety rule then your stunt group runs a lap. Out of 35 girls, 4 parents have complained. Is this too harsh?