From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Shao was a big brute and tended to start fights. He was enemies with the Chin-Star School, but he eventually became friends with Son Goku and the school after Goku defeated his brother in King Wonton's Royal Match. Shao accused Chin Taiken's son, Chin Shoken, of stealing his wallet. Chin was forced to defend himself and his son. Chin lept into the air and performed his trademark move, the Phantom-Star technique, but started coughing. Shao took advantage of this and started to beat Chin. Ten Long then showed up and slapped his brother, apologizing for his brother's rude behavior.
When Goku passed by the restaurant where Ten and Shao happen to be eating at, Shao attacked Goku. Goku dodged Shao with ease and tricked him into falling into a river. Ten was not pleased and hit Goku without warning. Back at the Panther-Fang School, Shao watched his brother's pupils become punching bags as he tried to give them a lesson in combat. Later, after Goku had beaten Ten in King Wonton's Royal Match, the Phantom-Fang School and the Chin-Star School finally put the past behind them as Ten Long and Shao started anew under Chin as members of the Chin-Star School.