Alex rider - what happened?

Chapter 14

They were in the car on the way back home when Yassen suddenly remember what he wanted to ask Alex. "Alex?"
"Hmm?" Alex said turning to looked at Yassen glanced at him before looking back at the road. "Today in school, the kid called you druggie. Why?"
"... I was always away on mission. When I go back to school, I would always be injuries. They spread rumours saying I'm a gangster and get into fights. One rumour led to another." Alex said with a shrug as if it was no big deal. Which really isn't a big deal. "Actually... I might have to start skipping school again."
"Why?" Yassen asked. "MI6."
"What?" Yassen asked confused. Didn't Alex already say he didn't want to do anymore missions? Alex explained about MI6 wanting to hire other children to do their dirty work. Alex didn't want other kids to go through what he have. It's painful and it's no fun that's for sure. Not like what the kids would imagine. This ain't James Bond.
Why is this kid so selfless? Why can't he think about himself for once?