From: https://www.dol.gov/general/topic/youthlabor/agerequirements
The Fair Labor Standards Act (FLSA) sets wage, hours worked, and safety requirements for minors (individuals under age 18) working in jobs covered by the statute. The rules vary depending upon the particular age of the minor and the particular job involved. As a general rule, the FLSA sets 14 years of age as the minimum age for employment, and limits the number of hours worked by minors under the age of 16.
Also, the FLSA generally prohibits the employment of a minor in work declared hazardous by the Secretary of Labor (for example, work involving excavation, driving, and the operation of many types of power-driven equipment). The FLSA contains a number of requirements that apply only to particular types of jobs (for example, agricultural work or the operation of motor vehicles) and many exceptions to the general rules (for example, work by a minor for his or her parents). Each state also has its own laws relating to employment, including the employment of minors. If state law and the FLSA overlap, the law which is more protective of the minor will apply.
Posting requirements: Nonagricultural employers must also post the Labor Department-issued Minimum Wage Poster listing minimum age requirements in a prominent place at the worksite.
The following links will help in determining whether a particular job is covered by the FLSA, whether any special conditions apply, and obtaining additional information, including state law, relating to the employment of minors.
Child labor laws vary from state to state. Please consult your state department of labor for this information.