A: Well, they can be - but see it from their point of view. You're 12, going on 13, and puberty's kicking in. How do you cope with the growth spurts, bodily secretions and odours, the spots, a breaking voice (if you're a boy)? Even if none of these has happened yet, you feel just as bad because you think you're being left behind. Your parents expect you to behave more like a grown-up, but won't give you the freedom you want. Anyway, you don't have the money to support your independence. You're not even a proper teenager. If you're a boy, you're suddenly competing with people who used to be your mates. If you're a girl, you either belong to a little clique or you're emphatically outside it - and it's a struggle to keep up your social position.
You're in educational limbo. You were pampered and supported in Year 7, but now you have to look after yourself and show how much better you are than the new kids. You have no immediate educational goal as Sats are a long way off, so why bother?
If you had to cope with all that, how attentive would you be? Put yourself in their shoes before being too hard on them. Be sympathetic but firm - you're probably one of the few reliable, fixed points in their lives, and they need that stability. Don't let their gaucheness and their misplaced assertiveness goad you. Be patient, play the long game - they'll grow out of their awfulness.