There was no other reason for this. The principal and Lu Qing's grandfather were old comrades. However, the principal later switched to politics and was transferred to the education Bureau. Now, he was assigned to be the principal of this school. He was very open-minded and his attitude in school was not dogmatic.
Lu Qing obediently admitted his mistake. He listened to the principal's advice on how to study hard and not be too impulsive. Finally, after showing some concern for old Master Lu's health, he let Lu Qing out.
Of course, Lu Qing knew that this would be the result. He was not stupid. He would be a fool if he was punished for the sake of clarifying a rumour. However, this matter would definitely be reported. The principal would tease him for a while and at most, he would be scolded by his grandfather and told to stand by the corner as a punishment.