Richard Wilson, a Chelsea native who has been involved with the Boston-based Tenacity program since it started in 1999, helps kids at Voke Park last Friday work on their net game during one of the sessions. Tenacity has long been asked to expand to Chelsea from their 18 Boston-centric programming sites, but it never worked out. This summer, the time was right, and Tenacity and the Chelsea Recreation Division has enjoyed a great partnership so far teaching children the game of tennis, while also having reading breaks mixed into the day.