The Truth About Rats — Jacqueline Pearce

Unlike his perfect older sister, Jenna, Conner hates his piano lessons and gets bad grades in math.

Conner's really good at bike tricks and he loves animals, but his parents have a no-pets rule and they don't take his bike-riding seriously. When the local animal shelter gets overcrowded, everybody in Conner's pet club agrees to take in a foster pet. Conner has to hide his rat, Oscar, from his family, who would never believe that Oscar is smart and cute and pretty lovable. Or would they?