When I was a boy scout some of the scouts snuck in booze. It wasn't pretty. You have to remember that the leaders are fully responsible for the safety of all children and also liable. If someone cooks in a tent and sets a fire ablaze - leaders are ultimately liable. Everything might lead to a court case and in that situation then heck yes, they can search bags and tents. Otherwise, if the leaders have nothing but legal exposure, no leaders. School is the same way.