Don't feed the ducks

I saw him daring to walk on the frozenlake an felt like fear in his place . It is verry risky to walk on ice nowadays. When we went a bit further we saw a group of youngsters who are a bit mentally handicaped . He was one of them. Their tutor was shouting at him to leave the ice , and asked him what was written on the board nearby? The boy answered in a smart way " It is forbidden to feed the ducks " . That was a smart answer in stead of saying " it's forbidden to walk on the frozen lake" .