This is normal. When people reach puberty, their temper will become grumpy. At this time, it is also a rebellious period. He will feel that everything is unhappy. I advise his parents to be more patient, but not to nag often. Because of his bad temper, his parents' nagging may make him more bored. I am in adolescence now, and I learned about it through myself and my friends around me. I also asked the teacher this question, and the teacher said the same thing.