Welcome to Mastery Charter School John Wister Elementary. We could not be happier to welcome the 400+ Wister families that fought so hard for Mastery to serve their children. Serving students in Kindergarten through sixth grade, Wister will open in the Fall of 2016 as a Mastery Renaissance School. Students will engage in a joyful school day, rich experiences and have rigorous academic courses to prepare them for a lifetime of achievement.