Boys have been banned from a national netball competition, meaning many who have trained all year will miss out.
The Urdd National Sports Festival takes place in Aberystwyth in May and primary schools were told two weeks ago.
Organisers said it was aimed at encouraging more girls to take part while boys’ physical strength sometimes put them at an advantage.
But girls will be able to play in the football competition with boys at the same tournament.
Urdd Gobaith Cymru was set up in 1922 to provide opportunities for children through the medium of Welsh.
The sports festival is one of many annual events it puts on.
Ysgol San Sior, in Llandudno, Conwy, won the county tournament last year and competed in the national competition.
Pupils at the school have criticised the move.
“Netball isn’t just for girls, it’s for boys and girls,” said Mason, 10.
“If they’re taking away netball from the boys, why don’t they take a sport away from the girls?”
Ryley, also 10, said the move deprived boys of a new sport, adding: “I’m normally a football person, but I wanted to try something different.”
“If girls are allowed to play football, why can’t boys play netball?” said Florence, 10.
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Teacher Lisa Jones said the school still planned to enter a team but it would now include girls from younger years.
She described the ban as “a bit of a shock”, adding: “As far back as I can remember, we’ve been allowed to take boys to the tournament.”
Pupils wrote to organisers, saying how disappointed they were.
A statement from the Urdd said: “There is a significant gender gap in sports participation between boys and girls.
“Through offering an all-girls tournament with a clear pathway for continued participation we are actively taking steps to close the gender gap in sports participation.”
It added there had been complaints boys had been placed in “key areas” of the court where their “physical and athletic presence is an advantage”.
With the competition open to years five and six, the age gap could be from nine to 11-year-olds.
Organisers said they will review how the competition goes before making a decision about 2020.
Welsh Netball’s chief executive Sarah Jones said the rules of netball state it can be played by same gender or mixed gender teams.
But she added: “Netball is one of the few team sports to attract girls and women to participate in particularly large numbers, which contributes to address the global disparity in sports participation.”
Ms Jones said there had never been a demand for boy to play before, calling this “a whole new territory”.
“I think it’s an exciting time for the sport, that it is now starting to attract the attention of boys,” she said.