For my allstar team, in the summer, they are more lenient because of vacations and such, but you still need an excuse why you are not there and need to notify the coaches. If your sick, they usually ask you to come in anyways and watch practices, unless you are contagious or its reallly bad. But during competition season, the coaches, and the team, do not like it when we miss practices. If you miss any practices in the 2 weeks before a competition, if they can find an alternate, they will replace you for that comp. If it is not 2 weeks before a competition and you just don't show up without calling or anything, they call you on your phone, and make you come in and pay for an extra tumbling class.