dude, dont be afraid to be "aggressive", although in pickup your never aggressive, youre assertive. if you avoid this, you will come out as a wuss.
the first rule of pickup is: DONT BE A WUSS
and to ur question, this isnt a cold approach, therefore this isnt really an "opener".
to do a warm approach, open with what you have in common.
in this case, school (obviously).
now imagine a super alpha natural guy, who goes on facebook, and sees someone from his school, whos still studying there and whatever.. what would he write her?
i would imagine sumthin like "heyy whatsername, u guys taking care of the school for us?"
whatever you imagine, be that super alpha natural guy, and do what he would of done
(i call this the fight club effect

)
good luck my hindu friend