It happens more often than you think.
If its a high volume school they can't afford the plane off line for 1-2 weeks while it gets fixed.
So they prefer to get rid and usually rip the student off for the rest of the course fee claiming its insurance excess. Another reason not to pay upfront.
There was one when I did my PPL although that wasn't due to crashing it.
Although with some schools I have heard of incidents where the nose wheel has colapsed and its blatantly obvious that it was due to a previous incident un reported and it was just that poor sods luck that it failed on that landing.