A teacher has been disciplined after a pupil, who weighs 12 stone, claimed he called him 'Mr Blobby' in front of his classmates.
The 12-year-old said he was in a drama lesson at Lewis Boys School in Pengam, south Wales, when teacher Anthony Ager was trying to quieten the class.
He claimed that Mr Ager used the term 'Mr Blobby' after he spoke out in defence of a friend.
The boy's parents, from Bargoed, have been sent an apology by the school.
The boy said everyone laughed when the alleged incident took place but he felt "terrible".
He said: "He (Mr Ager) blamed one boy for making a noise but all I said was that it wasn't him but someone else who was shouting.
"Then he said: 'OK thank you Mr Blobby'."
Other children in the drama class have been interviewed by staff at the school about the incident.
Some pupils confirmed that Mr Ager had said 'blobby' but other children said they believed the term he used was 'gobby'.
The boy's father said it was a "disgusting thing to say to kid in front of all his friends".
"He's a big lad for his age - he takes after his dad because I weigh 18 stone," said the 45-year-old.
"But that's the sort of name you would expect from a bully in the playground not from a teacher in the classroom."
The former miner said his son was very upset.
"I kept him off class until we got an apology."
In a letter to the family, head teacher Dr Christopher Howard said evidence showed that an "inappropriate comment" was directed at the child.
"The evidence is unclear as to whether your son was called 'Mr Blobby' or 'Gobby'," he said.
"The two words sound the same. I believe that both phrases are inappropriate given the age of the boys concerned.
He added that "appropriate disciplinary action" had taken place.
"The pupil has been caused some embarrassment for which we apologise. We hope he will get over it quickly."
"The member of staff has been disciplined but the nature of the punishment is confidential," he added.