Children from low income and lone parent families are failing to make the grade in maths, a new report revealed today.
Youngsters who play computers games for an hour or more a day are also getting lower results in the key subject.
Around 4,100 forth class pupils sat a maths test for the Counting on Success survey, with their parents and teachers also questioned about their roles.
It found lowest scores were achieved by pupils who did no mathematics study and those who spent between one and two hours a day playing computer and console games.
Pupils' confidence in their own maths ability came from their parents' involvement in the school and families who integrated the subject into everyday activities in the home.
Results showed students with access to a computer at home scored well, although those with a computer in their bedroom scored less.
It also emerged that students having after-school maths lessons scored a lower mark in the test, with the highest scores achieved by those who spent up to two hours per day on sport or reading for enjoyment.
Family life and gender was also scrutinised during the survey.
Female pupils worked well with limited supervision and enjoyed the subject more, while males were more confident in their mathematics ability.
Members of the Traveller community and students with no siblings, or with four or more siblings, had lower scores.
"Children's ability to use mathematical skills is vital to ensuring Ireland's continued development as a leading knowledge-based economy," said Minister of Education Mary Hanafin.
"One of the most interesting findings of the study is that pupils who spend considerable periods using video games or playing with games consoles have lower achievement in mathematics than children who read at home, play games or undertake other pastimes.
"It is important that parents encourage their children to benefit from a balanced range of activities that contribute to their overall development."
The report is the fifth in a series of national assessments of mathematics achievement in primary schools and was carried out by the Educational Research Centre on behalf of the Department of Education and Science.