More than half of teachers believe that children with no internet access are seriously disadvantaged in their education, a survey has suggested.
A fifth of the 585 teachers surveyed for the Times Educational Supplement and charity E-Learning Foundation said internet access was essential for pupil's homework.
The charity also warned it was seeing support from the government cut.
It is estimated two million children live in homes without internet access.
An increasing amount of schoolwork, especially at secondary school, is dependent on computer use.
Some 55% of those surveyed said children who had no internet at home were at a serious disadvantage.
Chief executive of the E-Learning Foundation, Valerie Thompson, said the digital divide was having a damaging impact on children's prospects.
"Young people without access to the internet can struggle to complete their homework and coursework, and fall behind.
"Teachers are increasingly assuming that children have internet access, making it harder, and this can exacerbate the impact of the divide.
"If we are serious about improving the life chances of the most disadvantaged, we have to tackle the digital divide, otherwise the poorest children will be left even further behind."
The charity helps ensure children have access to learning technologies.