With the rapid changes in the market and environment, teenagers are confronted with a range of development issues.Therefore,teenager engagement is essential in shaping their values and attitudes toward life. London Borough of Lambeth, located in south London, is an area of high ethnic diversity with a significant number of young people who are involved in local crime and gang activities. High Trees is one of the Charities that delivers a variety of youth activities to meet teenagers' personal and career related needs. This project seeks to build up the evaluation system for the youth program at High Trees and to improve its efficiency and effectiveness.