The Plot

1- Val the counselor is assisting each teacher, Mr Medulla, Coach Boomer and Mr. Boy. She's fallen hard for Mr. Boy, "If only he could guide more of these impressionable children!"
Her power's allow her to suppress super abilities. This suppression can last indefinitely IF she chooses to maintain it. At some point she'll be forced to take her turn watching detention (the courtesy class), which will break her hold on them.
She will choose several likely cases during power placement, then hold it.

-- why? pick boys? pick people she thinks need special help? Random? who she is next to?

2- Krag the simple thug has been looking to score something... maybe there is something he can steal and sell, maybe he's after the gravity displacer. Maybe he's after the detention center controls? Maybe he's just hired by the Ray as muscle.

3- The Ray, out to discredit Medulla or further his rivalry with Shard. Out to destroy Sky High
replace Principal Powers ... how?
replace students - subtle mind control or infiltration?
replace staff with robots

Valentina Zambrovski
he wants Val to suppress certainpowers. either to distract the staff, or to prevent his own detection?
or perhaps eventually to trick herinto suppressing Principal Power's own pwer, allowing kidnapping, or other havoc in the high school