Pupils will be able to get free sanitary products at all primary schools in England from 2020, the government announced on Tuesday, after warnings girls were being forced to skip classes due to being unable to afford them.
Officials said they decided to expand funding previously only offered to higher-level schools and colleges to include schools for younger children aged up to 11 after feedback from teachers, students and parents.
"This is fantastic news... Period poverty should never be a barrier to education," said Amika George, who founded the #FreePeriod campaign pushing for free menstrual products for schoolgirls from low-income families.
"With free access to menstrual products for every child in compulsory education, every student can go to school without the anxiety or stress of worrying where their next pad or tampon will come from."
Some 10 percent of girls in Britain have been unable to afford sanitary products, according to a survey by the children's charity Plan International in 2017, with campaigners warning many are forced to miss classes as a result.
Chancellor Philip Hammond last month announced funding for free sanitary products for students at all secondary schools and colleges.
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However, the scheme had not initially covered primary schools, with campaigners against period poverty warning that some younger children were also in need.
"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," said children's minister Nadhim Zahawi.
The Department for Education said the funding would be in place for primary schools from "early" 2020.