why do they do a background check after you finish school?

No, there is no drug screen to get a dot medical card, that is a myth. The urine test tests for blood and sugar in the urine for diabetes .

 

Dead on ...

 

Trucking companies operate according to its bureaucracy. A lot of them spend money to fly or bus people to oreintation before they finish employment verification, background check, mvr, etc. We all know they wait till you are in oreintation to do DOT physical.
I don't see how those companies that hire 20 people a week can afford to do it. 3 or 4 will be sent home in oreintation and 3 or 4 will be sent home in couple weeks after company discovers something they missed.