A decision to cut a £700,000 grant which helps thousands of poorer families buy school uniforms in Wales has been criticised.
The Welsh Government's school uniform grant, available to Year 7 students eligible for free school meals, helped 5,500 learners last year.
But it has cut the scheme for 2018/19, as the cost of uniforms had "reduced".
The Bevan Foundation said it was a "mealy-mouthed" justification for a cut that would save a small sum.
Dr Victoria Winckler, the think tank's director, said the grant was "not perfect" but the decision to end it was a "surprise".
"It's quite a big expense, especially if you've got more than one child," she said.
"And that comes on top of an expensive school holiday period, where you've had to pay for extra meals, and perhaps for entertainment and so on.
"For families that are already on low incomes, it can be a real blow.
"It's no accident that pay day loan companies are very active around that time of year, the start of the school term."
The scheme was introduced in 2005 with its latest incarnation offering eligible pupils £105 before they start secondary school in Year 7.
The grant has been administrated by councils, with parents applying to their local authority for the money.
Dr Winckler also called for low-cost uniforms to be available in supermarkets and other outlets, and to have sew-on badges.
Staff at Ysgol Friars in Bangor, Gwynedd, already buy poorer pupils items such as shoes they cannot afford, according to headmaster Neil Foden.
"Children can be very cruel to those who are somehow different," the NUT Wales chairman told BBC Radio Wales.
"If they are obviously different and dressed differently, it does draw attention."
He said the school was holding charity dress-down days but these have reduced, adding: "Children from poor backgrounds simply can't compete in the fashion stakes with their wealthier peers."
Mr Foden described the uniform as "eliminating differences between pupils" and said undermining it create divisions.
He added: "If children keep to the minor rules (such as uniform), they are less likely to infringe on the bigger ones.
"Uniform is a way of avoiding social stigma because they all look the same."
He blasted the "bonfire of grants" that have affected some of the most vulnerable school children.
Natasha Hayes, who volunteers at a community clothes bank in Cardiff, said people go in for donated school uniforms "on a daily basis".
"As fast as it comes in, it goes because it's really expensive to buy new," she added. "We've had people crying coming through the door, saying they can't afford it."
She said she was not sure hard-up parents even knew the grant scheme had been available.
Rebecca Derrick, a single mother-of-three from Port Talbot, said the decision meant she would struggle to buy new uniforms for her children.
"The school have offered to buy trousers and shoes, but my pride is there, and I don't want that," she said.
"Even the £105 per eligible Year 7 child provided by the grant was barely sufficient to buy a full uniform and PE kit."
In England and Scotland, school uniform grants are offered on a discretionary basis by local authorities with the latter having a national minimum suggested by the Scottish government.
The Northern Irish government funds a £3m scheme which has been taken up by about 98,000 pupils.
The Welsh Conservatives said the move "will hit the poorest pupils the hardest".
The Welsh Government said many schools and local authorities in Wales have arrangements in place to support families struggling with the cost of uniforms.
A spokesman said: "Since the introduction of the grant... school uniforms have reduced significantly in price and their availability has increased.
"We have also worked with school governing bodies to encourage schools to follow Welsh Government guidance on keeping uniform costs low."
The Welsh Local Government Association has been asked to comment.