First of all, don't waste your money on modeling schools. Legitimate agencies don't require them. The only thing you should pay for are photos for your portfolio and composite cards. Contact a talent agency that books models. You can get started by giving them good digital photos. If interested they will schedule an interview.
Ask local hairdressers or stores if they need any models. Look out for local school or charity fashion shows in your area. Send a portfolio to an agent.
Teens can get jobs through modeling agencies such as Barbizon. Teens have to be accepted into Barbizon's program and go through classes before they move on to competitions. At Barbizon compeitions, representatives from many different modeling agencies watch the way participants walk on the runway and call them back after the show, if they like them, to offer jobs.