Dinner Ladies Don’t Count by Bernard Ashley.
"Jason comes to school in a foul temper. His teacher Miss Smith tries to deflect his anger onto the plasticine, but he isn't having it. He had come to school 'with a smack instead of breakfast' and all because mum has said he can't have a dog for his birthday. Mum has developed an allergy to dogs, but Jason is beyond understanding. He progresses to vandalising Donna's plasticine model, and then is accused of a crime he hasn't committed. Hauled off to the headmistress, he refuses to explain the real problem. An understanding dinner lady talks him round and back in the classroom he discovers what has really happened to the missing birthday cards. Succinct, but manages to get in all the right detail." - from healthybooks.org
There’s a photo of me somewhere reading this. I got it in an early Christmas book parcel and spent Christmas Day reading it. We still have it somewhere I think. I loved it.