Child performers in theatre are governed by 2 sets of rules: state laws and union rules (if the show is a union signatory).
True Broadway shows are in New York City, of course, and they fall under the 2003 Child Performer and Trust Act in that state. This law doesn’t do much to limit work hours or conditions, but it does require work permits, trust accounts and minimum educational provisions.
In Los Angeles and San Francisco, the California laws are the most strict in the nation. Plays must abide by the same strict standards as television and film production. This means a studio teacher 24/7, required school time each day and limited work hours. For this reason, shows based in Los Angeles are few and far between, and parts for kids are almost always double or triple cast.
Touring companies are a free-for-all in terms of laws. Since no state really claims jurisdiction, the only protections come from Equity, the union. And then, only if a tour is a union signatory.
As mentioned above, the union covering most live theatre is Actors Equity Association, AEA or just “Equity” for short. If your show is union, there will be union contracts that govern the show for things like safety, minimum wages, etc. Contact Equity and ask what scale is for the contract that show works under. Then check the Equity site for the contract, here:
There are stage shows on Broadway, in theme parks (Disney and Universal Studios for example) and in circuses that fall under another union, AGVA. AGVA is the American Guild of Variety Artists. These shows have similar safety protections for young actors, but they pay far less than their Equity counterparts.
Before you audition, make sure to check the laws for the state in which you will be performing. Then check the union status of the show.
Union vs. Non-union, to Join or Not to Join
Joining Equity is definitely the mark of a professional theatre performer. Once you join the union, you will need permission to do any non-union shows. So make sure you are ready to make the jump into the professional world before joining. In Equity, age 14 is magical, since they have separate joining requirements and will often grant permission for under-14s to do non-union projects. After that—be prepared for no participation in high school musicals and community theatre.
Keep in mind that although you might have a local Equity theatre, most of them have a limited budget and thus a quota of Equity contracts. They will almost never use an Equity contract for a child. Having an Equity card in these situations can be a detriment for a child.