it depends on what type of cheer squad. for a jr. high i would say about 16 , for high school about 20 , for allstar it can be anywhere from 16 to 40 and for college about 20 also. it usually depends...
You can go to varsity.com and they have a list of National Cheerleaders Association camps and Universal Cheerleaders Association camps for summer and I think through competition season as well.