The food campaigner School Food Trust believes that UK parents are being given confusing messages about registering their children for free school lunches by schools and the government legislation that instructs them.
Currently, the government says that parents should sign up for the meals even if their children "are not going to have them", reports the BBC.
With the emphasis of this message being on the fact that schools receive an extra payment for each child registered for free lunches rather than the benefits of the children eating lunch, the School Food Trust believe that this is wrong, saying pupils who eat lunch are more attentive in the afternoon.
Judy Hargadon, chief executive of the School Food Trust, said it was vital that poor children ate the meals.
Last year, the government have launched the Pupil Premium, which is extra funding paid directly to schools to pay for school meals.
"If your child is eligible for free meals, it's worth registering them even if they're not going to have the school lunch," says the Pupil Premium.
However, many believe that under this the parents disadvantaged children are being given shortsighted messages.
Ms Hargadon said agreed that while the policy was "a brilliant idea", she added:
"We are very concerned when we come across examples of schools saying you don't have to eat the meals.
"That indicates to us that they are not registering the importance of children getting these meals.
"For some children, a school dinner is their only, or main meal of the day."
By not stressing the health benefits of eating the meals, she thinks that schools are being short-sighted and "missing a brilliant opportunity".
After all, pupils who eat the meals not only would the schools get the Pupil Premium money but, she said they would be getting "more attentive pupils in the afternoon, pupils who are fit to learn".
"It's a very confusing message for people," she added.
A government spokesman said:
"We want every child eligible for free school meals to sign up for them – so that pupils benefit from a healthy school lunch and schools receive all the Pupil Premium funding they need to support them."