Results of the Key Stage One assessments, made when children are seven, show that the proportion reaching the required standard in reading, writing, maths and science falls well below other children.
The Department for Education identifies children from disadvantaged backgrounds as those who would be eligible for free school meals.
These children are lagging behind in all the assessed topics.
The biggest gap is in writing with 47 per cent reaching the required standard compared to 71 per cent of other children.
In reading, it’s 54 per cent compared to 77 per cent.
Fewer children receiving free school meals met the standard in maths and science too.
Nansi Ellis, assistant general secretary of National Education Union (NEU), which represents teachers, said; “There were 4.1 million children living in poverty in the UK in 2016-17, according to Child Poverty Action Group – one in four of the school population.
“Any serious strategy for raising educational attainment has to address these appalling figures.
“Teachers are working more than 50 hours a week, and this figure is rising, but there are limits to what can be achieved through placing the responsibility of lifting standards on schools.
“There are wider issues which need to be addressed, and the Government is not addressing them.”
Assessments were made of 9,835 pupils in state-funded schools across Nottinghamshire.
The proportion reaching the standard in reading was below the average for England, but ahead of the regional average.
Girls performed more strongly than boys and the gap was widest in writing where girls were 16 percentage points ahead.
In reading, 79 per cent of girls achieved the target standard, compared to 70 per cent of boys, and 27 per cent of girls were judged to be working at above the required level.
The Key Stage One assessments were introduced in 2016 to determine how children were coping with the more challenging national curriculum set by the Government and the increase in the standards expected.
The NEU says that looking at how children are learning is important but Key Stage One assessments are a poor way to do it.
Ms Ellis said: “We don’t need to test every child in high-stakes ways that put a lot of pressure on them, in order to evaluate whether a school is doing its job.
“Other countries have found different and more successful ways of monitoring the quality of education and improving it.”
Nick Gibb MP, Minister for School Standards, said: “Reading and writing are the foundation of education and once grasped can open up a world of literature and knowledge to young people.
“We remain determined to make sure that not just most children, but every single child is able to meet his or her potential.”