When a boy's voice 'breaks' it can be very upsetting for him until it settles down again into his adult register. It usually happens between the ages of eleven and fifteen and can be sudden or gradual. Male vocal chords more than double in length, the voice box tilts to create the distinctive 'Adam's Apple' and facial bones grow leaving bigger resonating spaces within the face.

The result of all this is that the frequency of the vibrating vocal chords may go from 200 times per second to around 130 - slower and deeper.
Sometimes to avoid adding to the embarrassment of random squeaks or croaks, teachers just excuse their students from singing temporarily until it sorts itself out, but some authorities recommend that a boy doesn't sing at all for up to five years until his voice has completely settled down. Probably, most would opt for a compromise because there is a serious danger that if boys do stop singing at this critical time, they may give up completely.

Teenagers have enough to cope with without this extra worry, so reassurance has to be very important. As a parent, carer or teacher, try to prepare them for it so that it doesn't come as a surprise. Explain the physiology. Tell them that it happens to every young man and that it won't last for long. Not to worry if it hasn't happened yet - Aled Jones was sixteen when his voice broke - and if they're still anxious, encourage them to have a chat with their GP.

Keep them singing a little and experimenting so that they can look forward to the voices they're going to have. Choose your material carefully - maybe fall back on some sea shanties or something like Coleridge Taylor's Viking Song. If they were standing among the sopranos, let them move over only when they feel ready. Support from peers is very important so get everyone involved to accept it as normal and enjoy the outcome. Added bonus - maybe you'll get that extra tenor you were hoping for...