I'm wondering why is it so hard to get a clear positive ID on all the fatalities in this case? Unless there is a suspicion of something truly diabolical - switching clothing or bringing other children to school who aren't students there in order to kill them, it seems it would take me under 2 hours to have a firm, positive ID on all 30.
Anyone who has ever gone on a field trip with a class knows a school can tell you immediately which kids didn't get on the bus that were expected - and a teacher could simply look at her class roll, parents can pick up and sign out their kids, and those who weren't picked up are the pool of names you draw from.
Why in the world is it taking so long? This must be agonizing for the parents.