How do you keep your kids (7yo) from lying?

It’s always been my policy that a lie is worse than the original issue. I grew up in a strict household with lots of punishment for mistakes, but I was also taught that lying was sooo bad. It’s helped me be honest my whole life. I had a kid go to the nurse, and the nurse told me he smelled bad. She asked if he needed a shower (we don’t have them at school, but he could if he wanted), and the kid said, no, I’m fine. (He was fine) Then he came back to class and told me an elaborate lie about the nurse saying he needed a bath, she gave him the keys where he found a thanksgiving dinner hidden in one of the rooms, and then he ate the whole thing to prove to her that he wasn’t hungry. Then he got called out on the lie, and when disciplinary action was discussed, he told me more lies. I would say, “That’s not true.” And he would move on to the next lie. In the end, he apologized and admitted that he was lying. But how do you teach a kid not to lie, when they seem to have no qualms with it? This is a very challenging kid. He has one of everything: ADHD, OCD, Tourette’s, dyslexia, autism, epilepsy. <br><br>Edit to add: I do tell him that it’s okay to make mistakes. I understand that his brain works differently, and when we are struggling with a problem, we can get another brain on it. I also tell him that it’s okay if he gets an answer wrong. That’s why we ask questions.