Firstly I would ask why he is doing it, is something upsetting him, can you enlarge what he steals , sometimes children take things to show to others , without asking permission , you also say he is lying it would be good to know something about what he lies about. Could he be upset about a new sibling,(they can get jealous) change of school, home, family .How does he get on at school, has he friends are they good friends ...?