Make sure you take the opportunity to teach him whenever he misbehaves. For instance, if he comes home and says he does not have homework and then you find out that he actually does, talk to him about lying. Sit him down and briefly describe what he did wrong: “You told me that you did not have homework, but you do.” Then give him an appropriate consequence like you have been doing. Make sure that you clearly link this consequence to his misbehavior. Say something like, “Because you lied to me …”
After you have described the negative behavior and given a consequence, follow up with teaching. Tell him what you want him to do differently next time. Say something like, “Next time you have homework just tell me the truth. If you need help with it or if you need breaks, talk to me about it.”
Give him a good reason why it is important for him to tell the truth. This might sound obvious, but children aren’t programmed with reasons. Sometimes you have to explain even the simplest things to them.
If you consistently and patiently try to teach him and give him consequences without seeing any improvement, it might be time to talk to his pediatrician. There could be a medical reason for his misbehavior. Some kids who have ADHD, for example, are bright but tend to be class clowns. They also struggle with impulse control, which explains why some ADHD kids steal and lie. This does not mean that your son has ADHD, but it is a possibility. If not, your pediatrician can offer you further suggestions to rectify your son’s behavior.