A school is facing complaints for "preaching veganism" to its pupils and criticising the role of agriculture.
Wymondham High School has been accused of "ramming" vegan diets down children's throats and of closing down debate from those who objected.
It follows a Year 8 science lesson on climate change and a discussion about the contribution made by agriculture.
Jacob Lascelles, one of the pupils in the class, claims that during the lesson his teacher had "preached" to pupils about veganism.
The 12-year-old, who lives on a farm with his parents and has a pet cow called Blue, says that when he questioned the criticism his arguments were shut down.
He said: "The teacher said that adopting a vegan diet was the best way to prevent global warming.
"When I questioned that I was just told to be quiet and threatened to be sent out of the class if I carried on and that I was wrong.
"I was just trying to argue my point and put my views across."
Jacob's mother Rachael has complained to the school about the lesson.
Ms Lescalles said: "I was fuming when Jacob told me. I do not think schools should be preaching veganism to pupils as it is a personal choice they should be left to make.
"We live in a rural county where agriculture is one of the biggest industries and we provide some of the very best meat around here.
"Children should be learning about this and I would be delighted to welcome classes to our farm and share with them what we do."
Ms Lascelles added: "It is not fair for children to have something that is a personal choice, like veganism, rammed down their throats."
The Enrich Learning Trust, which runs the school, did not respond to a request to comment on the incident.
However, in an email to the family seen by this newspaper, a representative apologised for the upset caused by the classroom debate - and praised the youngster's "fantastic, contextualised examples" in discussions about farming.
In the email, a teacher wrote: "I believe this issue has arisen as Jacob's class are completing project work on everyday changes that they could encourage their peers to make to help reduce our impact on global warming."
The email went on: "Having taught Jacob throughout his key stage 3 journey, we have had many conversations about farming and he is often able to give the class fantastic, contextualised examples.
"Many of these, such as your sheep breed, have then fed into my teaching further up the school as local examples of topics we teach - please thank him for this."
The teacher added: "Thank you again for your support of Jacob's science education and apologies for the upset caused."
While environmental scientists do largely agree that reducing meat consumption will cut carbon emissions, experts are divided on the extent of this.
Some studies have suggested that halving meat consumption could reduce emissions by up to 30pc per person, while others suggest choosing vegetarian options will only cut these by 3pc.
The contribution of the agricultural sector to climate change is a hotly-debated topic, with pressure regularly applied on farmers to look for ways of reducing emissions.
The National Farmers' Union has set the industry a goal of being net-zero greenhouse gas emissions by 2040, with many technological advances to offset the impact already being adopted locally.
It is not the first time Wymondham High School has become embroiled in a public controversy involving criticism from parents.
A year ago, the school faced complaints after changing its uniform policy to allow boys to wear skirts - but not shorts - in hot weather.
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