sentences:  He became Chairman of the Headmasters' Conference Eastern Division in the 1970s and broke new ground by inviting the heads of the Girls' Schools Association to attend HMC meetings.In 1977, he argued that five subjects, rather than three, should be taught in sixth forms, and that this could be made possible by universities teaching more inter-disciplinary and creative courses.Lockhart retired as Headmaster of Gresham's School at the end of the Summer Term of 1982.