I have a cousin who got good grades in high school. After the college entrance examination, he was admitted to Tsinghua University. As a result, he only attended school for two years and was dismissed from school.
Later, I learned the reason, because my cousin was too bitter in high school and neglected discipline when he went to college. He plays games every day, and sometimes he often skips classes. After a year, he failed so much that the school gave him up and advised him to leave.
Fortunately, when he was about to drop out of school, he pulled back from the brink and studied hard. He didn't fail in the exam that year, but he did well in the exam, so the school gave up and advised him to drop out.
Generally, students who are dismissed from school either have good academic performance but are unwilling to study, or they just idle around all day.