Greenside High School is a public co-educational high school in Johannesburg, Gauteng, South Africa.Greenside High School (Top Public School in Gauteng 2007) is situated in the suburb.Notable alumni James Small, rugby Claire Johnston, lead singer of Mango Groove Candîce Hillebrand, actress and singer-songwriter Trenton Birch, singer of Trenton and Free Radical Alistair Cragg, is an international track and field athlete