Some of the most deprived children in England will miss out on the Government's flagship pupil premium because their parents are not social security claimants, The TES has learnt.
Schools that teach pupils from poor families who are not able - or are unwilling - to claim benefits do not qualify for the pound;430 cash allowance, which is designed to give them extra support in the classroom and improve performance.
Experts believe the group most likely to suffer are children from Gypsy, Roma and Traveller communities, who already underperform in all educational measures.
Politicians and charities are now pressing the Department for Education to review the rules.
To qualify for the extra cash for their pupils' schools, parents must be in receipt of benefits, including child tax credits. But many travelling families, particularly economic migrants who have moved to England from countries in Eastern Europe such as Romania, are not entitled to benefits because they have not been in permanent employment or work as casual labour in industries such as agriculture.
Their representatives also say that some families in the Traveller and Gypsy communities choose not to claim because they consider benefits demeaning.
Other support for these groups is also being cut - including ethnic- minority achievement grants and Traveller education services.
Bradford East MP, Liberal Democrat David Ward, who became aware of the issue in his constituency, is now gathering evidence to pass on to the Government.
Mr Ward said that his local schools were doing a "brilliant job" with newly-arrived Gypsy, Traveller and Roma pupils, but would now face real- terms funding cuts because they were unable to claim the pupil premium.
"In inner-city Bradford there are between 30 and 40 schools that have about 50 to 60 children in this position," he said.
"They are not going to want to take them if they don't qualify for the pupil premium," he went on. "It will be hugely divisive not to include children from deprived backgrounds who don't qualify for free school meals (FSMs)."
In evidence given last year to the government consultation on the pupil premium, Linda Lewins, vice-president of the National Association of Teachers of Travellers, predicted that Gypsy, Roma and Traveller pupils would have "difficulties" accessing the benefit.
She called for them to be "treated as a separate group", like looked-after children, who automatically qualify for the premium, and pupils from service families who will get their own version of the pupil premium.
"The FSM indicator is problematic. Some families do not claim FSM either because they are not eligible or because they prefer not to. Gypsy, Roma and Traveller children on FSM seem to outperform those who are not which implies that other factors than deprivation apply to them," she wrote.
Debbie Harvey, co-ordinator of the Children's Society's Gypsy, Traveller and Migrant Children's Project, told The TES that she was lobbying the DfE to extend the pupil premium to children from travelling communities.
"They have some of the lowest educational outcomes and are far more likely to be excluded, and not all get free school meals. This can be either because their family is too mobile and they don't stay in the same place for long periods, or because their family is too proud," she said.
"Claiming for benefits isn't part of the culture. Yet the pupil premium would bring schools more money and resources which would go a long way to improving their circumstances.
"Traveller education services are under tremendous pressure because of local government budget cuts. We hoped the pupil premium might have mitigated that."
To claim benefits in the UK, EU citizens have to be "habitually resident". They are not eligible for Jobseeker's Allowance unless they have worked here for at least two years. Those not in work, and not seeking work, are not eligible for "income-related benefits" such as housing benefits or tax credits.
A DfE spokesman said:"The link between FSM eligibility and low attainment is proven and strong - that is why it is the best way to target the pupil premium at the poorest pupils.
"We also provide funding to local authorities, along with the flexibility they need, to support underperforming pupils."
Only about 80 per cent of Gypsy, Roma and Traveller pupils stay in school after 11, and 30 per cent attend more than one secondary school.
Only half of the children who do go to secondary school remain there until Year 11.
About a quarter of Travellers of Irish heritage, and 18 per cent of GypsyRoma pupils are classed as absent from school.
In 200809, the highest rates of permanent exclusion in England were for Gypsy and Roma pupils and for Travellers of Irish heritage, who are three times more likely to be excluded than the school population as a whole.