The seven students who overdosed on the Russian designer drug Phenibut have been expelled from their Gold Coast school after the final student was released from hospital at the weekend.

Six 15-year-olds and one 14-year-old were taken to Gold Coast University Hospital on February 21 after a mass overdose at Saint Stephen's College in Upper Coomera.

Four of the seven boys were in a critical condition, one was serious and two were stable. All have since been released.

In a statement, headmaster Jamie Dorrington said he had visited the boys at home earlier in the week and held meetings with them and their parents, which resulted in the boys' expulsion.