What does not suitable for children mean on drinks like mountain dew?

when it says not suitable for children what age does that actually mean because i took a bottle of mountain dew into school and this really bitchy teacher tied to take it off me because its not suitable for children, btw im 16 gonna be 17 in just under a month surely it means children aged around 10, ive been drinking it since i was about 12 anyway and im still here lol