Cutting the numbers of teaching assistants has had a “heartbreaking” impact on pupils, a primary school head teacher has said.
There are almost 1,400 fewer support staff working in Welsh primary schools compared with four years ago.
Jane Jenkins, head of Moorland primary in Cardiff, said she had to axe three out of 30 such posts with budget cuts.
The Welsh Government said it was making “the biggest single investment” in the school workforce since 1999.
Data from the annual school census shows there has been a 7.5% cut to primary school support staff from 18,655 in 2014-15 to 17,261 in 2018-19.
That includes the loss of more than 1,000 standard teaching assistants (TAs) and 300 special needs support staff, although there was an increase in the number of higher level teaching assistants from 1,128 to 1,435.
Jane Jenkins told BBC Wales Live that losing teaching assistants meant less one-to-one support for pupils for things like speech and language help.
“This generation of children has been let down by the system,” she said.
“It’s absolutely heartbreaking to think the interventions and support we were giving in the school 12 months ago, we’re no longer able to deliver.”
The adult to pupil ratio in her reception class has increased from 1:10 to 1:12, and she fears she will have to make further staff cuts.
“I’m really concerned about the future, I’m already dreading next year’s budget,” she said.
“I’ve been a head since 1997 and I’ve never known a budget settlement like the one we had this year.”
Rob Williams, from the National Association of Head Teachers Cymru, said recruiting and retaining important staff had become an “intractable” problem for schools.
“We know that schools are having to reduce the number of teaching assistants they have, or the number of hours TAs are contracted to work, because their budgets are at breaking point,” he said.
“It is obvious that until we address this combination of factors, and return to a situation where taking a job in a school is an enjoyable, manageable and decently paid career choice, the young people of Wales will always be losing out on their right to a decent education.”
In April, independent research found that school funding in Wales had fallen by £500 per pupil over ten years.
And an assembly committee concluded there was not enough money going into the education system.
But a Welsh Government spokeswoman said: “To help raise standards, we are delivering the biggest single investment in our workforce since the beginning of devolution.”
BBC Wales Live is on BBC One Wales and the iPlayer on Wednesday from 22:30 BST