For whom the Lord loves He chastens, And scourges every son whom He receives.
Hebrews 12:6, NKJV
It is quite an understatement to say that when children misbehave, they do not appreciate being disciplined by their parents, teachers, and coaches. Any punishment that might be rendered (such as grounding, spanking, or loss of privileges) will seem completely unfair. And yet, according to the writer of Hebrews, being chastened or scourged is a sign of love.
In the Roman world, some kids would be viewed as illegitimate, meaning that they enjoyed no inheritance rights at all. Other children had a rightful claim to the estate of their father. The writer of Hebrews is saying that a father would only love and receive and discipline the sons in the latter group. If God did not love you, He would not chasten you. The least loving action a parent can take is to simply let their children do whatever they wish.