I am a mom of a Middle School Cheerleader, and a high school football player. My kids have been playing Football and cheerleading ever since they were old enough to join. We have played in Celina when the field was so hot they said they could feel it buring their feet. But, neither of them would not leave the game. We kept them hydrated, found shade when we could take a break, and went right back at it. My daughter is every bit as tough as my son. (maybe more.)
She is also a competitive cheerleader, and I know the struggles of trying to get cheerleading recognized as a sport. If you are committed to a sport, you stay and see it through. They are part of the team, right along with the boys. I can tell you, that the girls that are really into cheerleading for the sport, will not want to leave. They have a job to do and they are committed to doing it. As long as those boys are out there playing in the heat, the cheerleaders need to be there to support them. Otherwise, they have just been robbed of the opportunity of being a real participant in the game, and a contributor to the game, and made a glorified fan.
Suggestion: If you are worried about the heat, and you have 30 girls, why not let half of them cheer at a time. Let the other half cool off, and then switch them out. But, they should NEVER leave the game before it is finished. Let's not go backwards in the fight of becoming a sport. Sorry coach, but all the parents on here are right. If they feel their child can't handle it, they can make the call to leave at that point. Same thing with the boys. I would love to see the football season switched with basketball, which is indoors. Then this wouldn't be an issue.