England's young children are being served "very small" school dinners, and given limited choice despite paying more for their meals, a survey of teachers suggests.
The poll reveals that almost a third of teachers do not believe that school meals are value for money, with some warning that pupils are often being given chips, pasta and rice rather than vegetables and salad.
It also found that there has been an increase in free school meals - a measure of poverty - as more families are hit by economic problems.
Parents that do pay for their child's meals are facing price rises, with a 50p per day hike costing families an extra £95 per child across the school year, the poll suggests.
The survey, conducted by the Association of Teachers and Lecturers (ATL) questioned around 500 school staff in England for their views on school dinners.
The findings show that nearly two thirds (62%) of teachers say the price of meals has gone up in their school or college this year.
Just over four fifths (82%) said the price had risen by less than 50p, while around 17% said it had gone up by 50p or more.
But more than a third (34%) said they do not believe the price of dinners represents good value for money, while nearly a fifth (19%) said the meals were not of a healthy standard.
A reception teacher from Bradford told the survey: "The younger children pay the same price but get much less [food] than the older ones. Also they do not get the choice as this is saved for the older ones."
One person working in early years education said: "The young children often get very small portions and very limited choice.
Children who come in with packed lunches eat a lot more at lunchtime."
And a primary school teacher said: "There are times that meals are good but others when they are most unappetising.
"There are occasions when the portion size is very small and there have been times when portions have run out."
One secondary teacher also told the survey that there seemed to be "a lot of carbohydrates" on offer.
"There are usually chips, pasta and rice available, while vegetables and salad don't seem to be on offer."
More than a third (36%) of those questioned said there has been a rise in the number of children on free meals at their school in the past five years, the survey found.
It suggests that this is down to the effects of the recession, and more parents facing redundancy.
A teacher in a secondary academy said "prolonged rural poverty, lack of job opportunities in the local area, an increase in single-parent families and home breakdown" were responsible for the rise, while a primary teacher added: "The intake of children from disadvantaged families has increased and Government cut-backs in welfare have not helped."
Around one in 10 (9%) of teachers said pupils eligible for free dinners in their school do not eat them.
Of these, almost half (44%) said they thought it was because pupils did not like the food on offer, and 41% said they believed these children prefer to bring in their own food.
ATL general secretary Mary Bousted said children were going hungry through lack of food.
"It is absolutely the case that children are going hungry in school, and we all know what hunger does to ability to learn," she said.
Dr Bousted said some teachers responding to the survey had warned that children do not get enough food, adding: "I think there are concerns about quantity and quality.
"Free school meals are very necessary, and a very good thing, but we could do with more consistency and more inspection of standards of meals, because if they're not inspected, then there's a danger that private market forces could take over, and you're getting as much profit as you can out of feeding the nation's children."
The survey comes as ATL members debated free school meals at their annual conference in Manchester.
Delegates passed a resolution recognising that a rise in child poverty will further increase the importance of school dinners and cooking skills for the health of children and young people.
It calls on the government to introduce a universal credit system to make sure that qualifying for free school meals becomes the accurate indicator of child poverty.
Clare Kellett, an ATL member from Somerset, said many schoolchildren do not need to read books by authors such as Dickens and Pope.
"They don't need to read about it to find out about child poverty," she said. "They are living it."
According to the latest figures from the School Food Trust, 79.8% of pupils registered for free school meals in primary schools were taking up their meals, compared with 79.3% in 2009/10.
In secondary schools, 69.3% of those registered took up the dinners, compared with 68.4% in 2009/10.
An estimated 1,055,000 free meals were being served every day in 2010/11, the trust said.
Michelle Smith, school projects manager at the Jamie Oliver Foundation, said they wanted to see an increase in actual take-up of free dinners.
"Not only do we want to see more families registering their eligibility for a free school meal but we also want to see that registration result in more children actually choosing to eat that meal every day and benefiting from it."
She said the Foundation was calling for a universal credit system that would make more families eligible for free dinners and allow schools to invest in a good quality meals service.
A School Food Trust spokesman said: "Every child's appetite is different so portion sizes aren't set nationally - but cooks do get to know their pupils, and should make sure they are getting a portion that's appropriate for them. If parents or teachers are ever concerned that children aren't getting enough to eat, we always advise that they talk to their cooks in the first instance."
She added: "School meals need to be affordable for families. Our research proves that school food is particularly sensitive to changes in price and in these tough financial times, access to decent food at school for children has never been so important.
"Schools need support to build their market, run their catering efficiently and to deal with rising costs."