Too Cool for School:
A state in which a person thinks him or herself superior to everyone else in a given group or in general. Most commonly used sarcastically. 
There is a difference between being ‘too cool for school’ (TCFS) and being snobbish, pretentious, conceited or even having a superiority complex, although being TCFS may at times incorporate those other repellent qualities.
There is a sense of being ‘above it all’… that just about everything and everyone else is somehow beneath you. Not in terms of social or financial standing for many of the TCFS come from quite modest, even poor backgrounds.
There is often a distinct gap between where the TCFS feel they should be and where they in fact are.
I’ve noticed many a waiter or waitress in artsy type restaurants and cafes adopt a tired, bored attitude when serving customers. An overwhelming sense of ennui engulfs them making it barely possible for them to do the menial tasks that cruel fate has inflicted upon their noble souls. Baristas (or baristards, as I sometimes call them) are quite often TCFS. In fact, being a barista is perhaps the ideal job for someone who is TCFS yet lacks any other marketable skill or talent.
Uh huh… Spare me the attitude and make me my cappuccino, ok?
The TCFS are at their best when they need something from us plebes. People with whom they would otherwise never be caught dead, let alone associate, suddenly become necessary. What to do, what to do? No problem. The TCFS make it seem like they are doing YOU a huge favour by allowing you to be of some small assistance to them.
“It would be really cool if I could use your cell phone. I’d use mine but international calls are way expensive!”
Oh, golly gee. COULD I??
Listen… you’re above it all. Fine. Too involved in the high drama that is your life to talk with the groundlings. Great.
Just don’t expect me to play along, ok?
Now get me my damn cappuccino!