My sons are between the ages of 11-13. We make them shower every evening esp on school nights. Let me tell you how much of a fricken hassle it is to get them to do it, even though they have done the same thing every night for the last 3 years or so. Even so, occasionally one slips by and with three of them sleeping in the same room, I walk in some mornings to wake them up and swear I'm in the cattle barns at the fair. When I was a teenager, we had one bathroom at home so I would wake up a bit early and walk to school just to shower.