St John's Grammar School is an independent Anglican co-educational early learning, primary, and secondary day school located in Belair in the Adelaide Hills, about 12 kilometres (7.5 mi) south of the Adelaide city centre.

The school offers a range of subjects to its students, who begin electing their courses from Year 8.

St John's has traditionally had a strong emphasis on music, winning numerous awards in this area.

The school offers a range of co-curricular activities, including various sports like soccer volleyball netball and sailing , music, debating, future problem solving, Pedal Prix, Duke of Edinburgh, and school productions.

The drama productions have included adaptions of well-known stories such as Little Shop of Horrors, Peter Pan and Charlie and the Chocolate Factory.