I've heard of this practice in TX.
Last year a team from TX attended the Christmas tournament of one of our local school's. As the officials were walking under the basket at one end and taking the floor a TX kid did a two-hand slam. He got Td. The coach told the crew that in TX the officials blow the whistle when taking the floor down there for this very reason. Apparently dunk season is open until that whistle sounds. As a courtesy our officials gave them a whistle prior to each of their remaining tournament games. It brought a smile.
Dunk season, Wabbit season, Dunk season, ...
