Must be just another "Active Shooter" Drill.
Nothing to see here, move along.
Buses have AIRBRAKES.
They are designed to LOCK upon loss of air pressure.
Thus, the bus CANNOT ACCELERATE.
Must have been some old buses.
I grew up in communist NJ in the seventies and eighties.
I've never seen a school bus without air brakes.
As an adult I drove a T/T OTR for many years.
Again, never saw a vehicle that was used for public transit WITHOUT airbrakes.