Trust me, making bombs is quite simple.
I have no doubt makeing a bomb is simple, but not as simple as picking up a gun.
And smuggling it into a school, is another thing,
And I believe the powers that be south of the border are on a watch for the purchase of large amounts of chemicals needed for making a bomb. After the first world trade center bombing and the Oklamhoma city bombing it is hard o stock pile large amounts of the chemicals necessary to make a big bomb,
so yeah you could make a small bomb, but smuggling it into a class room,
It is not impossbible but really, its pretty simple to pull a trigger, compared to making a bomb and delivering it.
And your chances or you odds of success really go down.