NC - Not allowed to clock in at designated times, wait without pay

[NC_Photographer]

Just a quick question here, and thanks for any and all replies. My son is 17 years old, a high school junior, and currently works for a nationwide "pizza" establishment part-time on the evenings and weekends. The work schedules are posted at least one week in advance, if that is relavant. He is routinely scheduled to work between 15 and 20 hours per week, but they do not always allow him to clock in at the appropriate time listed on the schedule.

For example, last night he was scheduled to work from 4 p.m. until 9 p.m. When he got home last night, he informed me that when he got to work, the assistant manager told him not to clock in because it was "slow", and made my son sit in the employee break room until just after 6 p.m. before allowing him to clock in and start working.

There have been other times when he was scheduled to work for four or five hours on a particular evening, yet they made him sit for two or three hours "in case they needed him", yet once they allowed him to clock in he only got paid for an hour or two. I have spoken to the managers and they claim my son is one of their best employees, so it doesn't appear to be due to a performance issue. My son says they do the same to most of the other employees as well. Is this legal for them to do?