"Nothing, probably saving on food costs."
According to the mum, the rule has actually been in place for a while but she only found out when her daughter mentioned the "disgusting" new sausages served at school.
"I only found out this week in an email.
"Amelia ordered sausage and mash and when she bit into her sausage she said 'eww'.
"Teachers said, 'oh, it's a vegetarian sausage' but they hadn't told her before she ordered.
"She ended up just having mash for her dinner. I'm fuming. She's been on packed lunches since," the mum wrote.
"I take it these children will never have a Christmas lunch ever again in school, something that's happened for decades and all of them look forward to," another parent wrote.
"Why not accommodate the veggies, vegans, whatever and add to the menu instead of making our kids adapt?
"And to request parents pack lunches that are veggie as well, not to mention the local farmers, this is absolutely ludicrous.
"No wonder my kids are starving and raid the fridge before the shoes are off," the parent added.
"Vegetarian is a choice for when they are older."
Other people wondered "what happened to freedom of choice?", while slamming the school for what they believe is overstepping the mark and trying to "dictate" the kids' diets.
Comments on social media also point out that the school is located in an area where farming is one of the main industries.
In the letter to parents last week, the school's head teacher Rachel Tomlinson said she had made the decision to offer only vegetarian lunches over a year ago to "stop climate change".
Her letter urged parents to send meat-free lunches to school, but the school is not enforcing that as a rule.
"If you still want to send packed lunches, could you please consider meat-free options to further support us in doing our bit to reduce carbon emissions as a school community?"
According to the head teacher, despite the disgruntled parents online, the school has received no complaints.
