My daughter was 16 when she got her job. Here, a child in school can only work 18 hours a week during school. No more than 4 hours on a school day and no later than 9:00pm on a school night. Holidays they can work 8 hours a day, but not past 9:00pm. In the summer they can work when ever and up to 40 hours a week.
Guidance offices are usually very stringent with working teens and if grades suffer they are supposed to be in contact with the parent. That is what good guidance offices do anyway.
I think it's great for her to work. I make sure she has everything she needs, and working ensures she has everything she wants.