First, I would highly suggest you contact your high school's cheer coach and see if cheerleaders are allowed to do both or how they feel about cheerleaders doing both. Same with your all-star program. Plenty of cheerleaders do both! My high school wasn't very flexible, but both all-star gyms I went to were flexible with school cheerleaders, so I think it worked out for girls who choose to do both (for example, letting them be excused from all-star practice if they had to cheer a game). Time management is up to you. I know girls who did both plus pre-AP/AP classes, and I know girls who gave up one because it was too much with school. If you really think you can keep your grades up, I say go for it. If you're unsure, it's not a bad idea to just do school cheer for one year and then decide next year if you think you can handle both.