How do Molly and Charlie gradually become distanced from Thomas and what is Thomas' response?

Molly and Charlie leave school and take jobs at the big house, which leaves Thomas alone most of the day. When they are all together, Molly and Charlie talk about grown up stuff from the big house and have no interest in school anymore. Thomas realizes that they are now a part of a world that he does not belong and that they are growing apart. He is not jealous or angry, just deeply hurt by the loss.