Do you know this book?

I was suddenly reminded of a book I read when I was about 12 today, but I can't remember the title!

It was about a rather ordinary boy whose last name began with the letter Z, and that was the focus of the story. How he'd always been last because of his alphabetical place. I remember he had a teacher that put the class in reverse order to make this kid feel more important. I also remember him being friends with a young girl who gave him a bubblegum stone (hopefully you know what I'm talking about if you read the book.)

I'd really like to find this book again, if you know the title that would be super helpful! Thanks!!