Dear Mrs. LaRue: Letters from Obedience School by Mark Teague

From chapters.ca:
When Ike LaRue is "imprisoned" at the Igor Brotweiler Canine Academy, he tries everything to get sent home -- weepy letters to his owner, even illness. In reality, Brotweiler is more like camp than prison, but still, Ike's not cut out for life without Mrs. LaRue and his creature comforts. Finally, he runs away only to find himself back in Snort City -- just in time to save Mrs. LaRue's life.