The filming at the Milton Abbey School in Dorset, which served as Bamfylde in the series, took place during actual school term. The "real" students at the school happily mixed with the cast and crew and many of the boys who appear in the series are genuine schoolboys.
At the start of Episode 6, after David learns the sad news about Beth and the twins, he walks outside to an isolated part of the school grounds, is eventually joined by Howarth, and then walks off alone to the nearby moors. What transpires so smoothly on film was actually recorded over several months. The scene with Howarth was shot in March, the scene on the moors in mid-May and the scene with David receiving news of the accident in June. Part of the problem was that the school used for the film was in Dorset, which doesn't have moors. Those were found in Devon.