It is terrible to fire her for that.
The parents did pay it the next day, so the school was not cheated.
She should have paid the $8 herself and let the parents pay HER back.
If she did not have concern of the kid paying it back, the better way is for her to use her own money and the kid then pays her back, not the school. Now all risk, however small, is assumed by her.
JoMa