Arrest those that hired them.
I had to go through a 2 month training program at Werner before they gave me the keys to a Freightliner. CDL school only teaches you how to pass the state test. That is when the state requires the test.
I was thinking more inline with fines and lawsuits if there were serious accidents involving illegal alien drivers.
That said, if illegal aliens work for or run the schools, then (if appropriate fed laws broken) then maybe arrests could be in order.