This was a children's book, or maybe for young teens. I found it in 2014 but it looked older so maybe it was written in the early 2000s or even later.
It was about a boy who falls off a cliff and passes away. His mother (who was maybe a scientist) buries him in some sort of acid which gives him the ability to wake up in different childrens' bodies. He had his teacher's phone number and would ring her every time he woke up. One day he woke up in the body of a a child who had an abusive father who cursed at him.
I’m not sure if I ever finished the book as that’s all I remember.