Broadcasting hours were for some time regulated by the British government, with some exemptions, for example, for educational programmes and sports coverage. The commercial broadcasters, therefore, reserved their most commercial output for peak viewing hours and used the remainder of their broadcasting hours to put out their contractually obligated programming, conveniently enough, at a time when children were at school. Networked programmes for schools and colleges were mostly made by the "big four" weekday broadcasters Yorkshire, Granada, Thames and ATV, and were screened during the late morning and early afternoon, after which the network would close down until children's programmes commenced in the afternoon.