You need to get printing quotes from several printers. The things you need to tell them to get the quote are the dimensions of the pages (you may want some guidance there from the printers on standard sizes—which will be cheaper), the number of pages (because of printing signatures (the press configurations) you will to increase pages in certain increments (again, the printer can walk you through this), and the quantity that you want to print in addition to that it is in color.
How to find printers. Check the phone book, read the ads to make sure they handle color. Then just go and talk to them or call them and have a salesman call on you. If you have a mock-up of the magazine that would be helpful to show them.
By 50 cents, did you mean you want that to be the printing cost per copy or did you mean that was the cover price of the magazine? If the former, that seems low unless you are printing an awful lot of copies. If the latter, does the cover price have to support the magazine or will you sell advertising?
Since it’s for a school, is it a non-profit project? If so, tell that to the printer candidates and they may give you a discount.
Good luck.