Yes, I've been around people who are high. Probably way more times than you have.
I've been high. More than once. There's no switch that goes off in your head and you don't know what the hell is going on. You still comprehend everything that is said to you, everything that you say, and everything you do. You make clear, concise decisions. You can act the same way high as you do sober.
The kids who act out of their mind are doing just that: acting.