Brasserie M&R - Men's room poster. 2016
Boys will be boys.
Prov. Boys are expected to be irresponsible or boisterous. (Also said ironically about men.) 
You can’t blame David for breaking the window with his baseball. Boys will be boys. 
My husband can’t resist driving eighty miles an hour in his new sports car. Boys will be boys.
(These are the 1st Israel Prime Minister David Ben Gurion and the 2nd Israeli President Yitzhak Ben Zvi, as Law students. Istanbul, 1912)