As many as you like, technically, up to 6, but remember, summer school is an intense and condensed format. Each class packs a year of learning into about 4-6 weeks of class time. You can't pass the class if you fall behind or run out of time. Each Summer/Recovery class demands 40-60 hours to complete (varies, depending on the class).
We recommend you take no more than 3 Summer School or Recovery Classes at a time.