A four-year-old girl was barred from eating a packet of chocolate buttons at her Cheshire primary school.
The school wants to encourage healthy eating
Zara Owen was stopped from eating her lunch box treat by a teacher at Dee Point Primary School, in Chester.
The school said sweets had been banned under its healthy eating policy because children were bringing in too many.
Zara's mum, 22-year-old Lucy Owen said parents should have the right to choose what their children take to school for lunch.
"I was absolutely disgusted," she told a national newspaper.
"My daughter has a balanced diet. She had eaten her sandwiches and yoghurt - so what was so wrong with her having the chocolate as reward for eating the rest of her lunch?"
She criticised teachers for telling her daughter not to eat the chocolates saying Zara was too young to understand and had returned home upset.
A petition has now been started by Mrs Owen to gather support from other parents who want to choose the contents of their children's lunch box.
No one from the school was available to comment but a spokesman for Cheshire County Council said: "School discipline is a matter for the school itself and each has its own set of rules which parents agree to when their children enrol.
"In this case, to support the school's healthy eating policy, sweets are not allowed.
"The action taken by the teacher was simply an attempt to uphold that ruling."
And chairman of the school governors, Tracy Coathupe, said: "On behalf of the school governing body I uphold the decision taken by the headteacher, as it clearly states in the school handbook that sweets are discouraged."