My 3 all have them at 19/17/13 -in the elder 2 rooms there isn't really a choice! Yes they can bang their head if they aren't careful, but they learn. If they area ilk theyhave camping Matt on the floor to sleep on
I've just ordered my almost 9 year old a mid sleeper with drawers and desk underneath. I envisioned her staying in it until her mid-teens at least. It's a full length bed. She has a tiny box-room bedroom so it makes sense.