If I was a good rebbe and I knew of a bad Rebbe, Id want him gone, Having 10 kids and no other Parnassah is no reason not to fire a bad rebbe. Not everyone is cut out to be a rebbe and If there is one bad Rebbe in a yeshiva of 20 Rebbes, that one Rebbe can spoil it for the rest.
If that one bad Rebbe teaches the same grade every year it means most of the boys will have that Rebbe and the entire well is spoiled.