Imagine, if you can, a PE teacher called Mr Dearling. This in itself is bad enough. Imagine further that Mr Dearling is very deaf in both ears. (You're getting it now, aren't you.) Thirdly, imagine that, due to his hearing aids, he can't hear anything said to him in a high register. Fourthly imagine how easy it is to scream without opening your mouth very wide. Finally, imagine a school gym containing fifty adolescent boys, running around in a big circle, screaming at the top of their lungs with Darling standing in the middle of it all completely oblivious. And, if you want to, you can imagine fifty boys all being put on detention when the headmaster bursts in.