Most teenagers want to have some kind of financial freedom. They want to have money, even if it means that they will have to work for it.
Working when you still are not an adult may turn out being a serious problem for your future. Teenagers must study! There must not have anything interfering in their school routine.
A part-time work may fully exhaust you in a week! Without even mentioning the stress caused by the though combination in trying to accomplish both school and work tasks. You will have money! But what about your future? What about your health? If you are working you are not studying.
To sum up it all I have to say that I do not agree with teenagers working part-time to earn money. They must study and have fun! As a teenager I know how exhaustive my days already are without working. It will not help them in anything and the money they will make is a fraction of the money they would make if they study hard for their future!