Girls in primary schools will receive free sanitary products from early next year, the government has announced.
The move comes after last month's announcement that the products would be made available in secondary schools, which was criticised for not going far enough.
But on Tuesday the children and families minister confirmed the scheme, fully funded by the Department for Education, will be extended to include younger schoolgirls.
Amika George, who started the Free Periods campaign, welcomed the news.
She said: "Free provision of menstrual products in all schools and colleges is something that Free Periods has been fighting for for over two years.
"Access to menstrual products for all children in compulsory education will mean that every child can have access to the products they need, and no-one will have to miss school because of period poverty.
"Every child should be able to go to school without wondering where their next pad or tampon will come from, and this will mean that no child will be held back from realising their full potential and being their very best."
In February research from the Bloody Big Brunch indicated that more than a quarter of girls or women have missed either work or school because of period poverty.
While it had been previously thought the problem had affected one in 10 women, the survey suggested that 27 per cent have at times been unable to afford sanitary products.
Announcing the scheme on Tuesday, Nadhim Zahawi said: "This Government is determined to ensure that no-one should be held back from reaching their potential - and wants everyone to lead active, healthy, happy lives.
"That is why earlier this year we committed to fully-fund access to free sanitary products in all secondary schools and colleges in England.
"After speaking to parents, teachers and pupils, we are now extending this to more than 20,000 primary schools so that every young person in all our schools and colleges gets the support that they need."
The scheme will be rolled out across primary and secondary schools early next year.