The student and his teammates were also targets of verbal abuse by Son senior, as reported by his family.
Son Woong-jung, Son Heung-yun and another individual were each ordered to pay three million won for violating child welfare law, Yonhap news agency and other South Korean media reported.
The three, who can appeal, have also been required to complete 40 hours of educational sessions on child abuse.
The Chuncheon District Court's decision on Friday followed the indictment of the three by prosecutors on August 30, who requested that the court impose fines.
AFP reached out to the court and the lawyers representing both sides, but did not receive a reply.
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Son Woong-jung has apologised but said the coaching staff at his academy "never spoke or acted in a way that wasn't rooted in love for the children".
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(Except for the headline, this story has not been edited by staff and is published from a syndicated feed.)