Parents climb through an overgrown garden to make their deliveries
Students at Rawmarsh Comprehensive are not allowed out of the grounds at lunchtime, so some parents are taking their orders for the chip shop instead.
They say pupils are not being given enough time or choice for their meals.
But the school said it aimed to provide good quality food that helped pupils to concentrate in the afternoons.
Julie Critchlow is one of the parents who delivers pupils' orders from the grounds of a neighbouring cemetery in Rotherham while the school gates are locked.
"The children aren't eating what the school provide in the cafeteria because they don't like the quality of the food," she said.
By the time the children have queued to get their lunch they haven't time to eat it
Parent Julie Critchlow
"They prefer to come to us to have their food delivered fresh and hot, which is what they're asking for. We're giving them what they're asking for."
The move is being seen as a backlash against TV chef Jamie Oliver's campaign for healthy school dinners.
But Ms Critchlow insisted it was not just about promoting junk food as they had several orders for jacket potatoes and salad sandwiches alongside those for burgers and fish and chips.
She said their actions had been prompted by the school's new half hour meal breaks, as pupils did not have long enough to eat.
"They're like caged animals at the moment," she said. "By the time the children have queued to get their lunch they haven't time to eat it."
From this term, pupils have been given two half hour breaks instead of the previous 15 and 45 minutes.
Parents say they have orders for salad rolls as well as burgers
Head teacher John Lambert said reorganising the school day and keeping pupils on site during breaks had already shown its benefits.
"Our motives are about effective education," he said. "Afternoon lateness has dropped to virtually zero and we know they are learning better in the afternoons."
He said he understood some pupils would resist the changes but believed that parents taking orders at the gates was undermining the school and their children's education.
"We aim to provide good quality food which is within government healthy eating guidelines and helps the children's learning in the afternoon," he said.
"The food that these parents are handing out is not part of a healthy eating diet and on top of that I have to question the morality of delivering it from the grounds of a cemetery.
"I just don't think it's helping their children and I don't think it's helping their children's school."
A meeting is due to be held between parents and staff next week to try to resolve the matter.
Schoolchildren at Rawmarsh Comprehensive School in South Yorkshire, England, are being fed fish and chips by their parents through the school gates at lunchtimes because parents do not believe their children are being given enough choice of food at lunchtime.

The parents are standing outside the school gates in a cemetery to take the orders of food from the children, and then go and pick up the food for them. Parents say that this is because the children do not like the quality of food being served in the school cafeteria, and so the parents are only giving the children what they want - which is a hot and tasty lunchtime meal.

Head Teacher John Lambert has lashed back at the parents, calling the delivery of food through the gates immoral and stating that it is not "helping the children or their school" by bringing the junk food in. He also stated that "The School aims to provide good quality food which is within government healthy eating guidelines and helps the children's learning in the afternoon". Parents have defended the delivery of food by saying that not only are they receiving orders for burgers and chips, but also for salad rolls, jacket potatoes, and other healthy foods.