One of the boys in my class has a big sister in third grade. Third grade has a much loved classroom pet, a guinea pig named Marshmallow. This family of four, sister, brother, mom, and dad took care of Marshmallow over the summer vacation.
Marshmallow is ailing. This family took Marshmallow to a veterinarian who said that the necessary surgery would be expensive, more than it would cost to replace the guinea pig.
The family was prepared to pay, after all, they informed the veterinarian, "Marshmallow is a classroom pet."
With that, the vet said, "I don't charge for classroom pets. The surgery will be free."