Published in 1977, Steven Kellogg's The Mysterious Tadpole is a delightful tale about a boy whose uncle (from Scotland) gives him a tadpole for his birthday. He takes the tadpole to school for show and tell, but it grows so big that soon, there isn't a place big enough for him.
Louis works hard to find a place for his tadpole (named Alphonse) that isn't a tadpole at all. He moves from a jar, to the sink, to a tub, and finally to a swimming pool, but the swimming pool is for the junior high, and when school resumes in the fall, he will have to find a new home for his pet.
I like this book because it shows a responsible pet owner. He doesn't just get rid of his pet; he tries to find a solution that works. He gets a job delivering papers to pay for Alphonse's cheeseburgers. Toward the end of the book when he can't figure out a way to keep his pet, he goes to the librarian for help because everyone should know that librarians are the ones to turn to for answers.
He finds a solution for a home for Alphonse, but you'll have to read the book to find out what he does with the the librarian's help.