Children should be seen and not heard... They agree!

Techno-savvy pupils have adapted the Mosquito alarm, used to drive teenage gangs away from shopping centres.

The alarm, which has been praised by police, is highly effective because its ultra-high sound can be heard only by youths, and some Grandmas, but not by most people over 20.
Schoolchildren have recorded the sound, which they have named 'Teen Buzz', and spread it from phone to phone via text messages and Bluetooth, yes, Bluetooth technology.
Now they can receive calls, texts and big-ups during lessons without teachers having the faintest idea what is going on.