There are fears councils are rushing to close rural schools before new rules that would protect them come into force.
More than 200 rural schools will be protected when a new code of conduct comes in this autumn.
But Llancarfan school, in the Vale of Glamorgan, is one of 10 set to close before then. Parents said the timing was "convenient".
The council however, said moving pupils to a bigger school was not a closure.
Changes to the Welsh Government's school organisation code - announced last year - mean local authorities will have to assess the likely impact of a school's closure, including on children's education and the wider community.
The Welsh Government has listed 219 schools as rural - 17.4% of all schools in Wales - but there are still plans to close 10 of the schools on the list, which is about 5% of rural schools in Wales.
Vale of Glamorgan Council is planning to "transfer" Llancarfan Primary School pupils to a new 210-place "super primary" in Rhoose, near Barry.
But worried parents in the village have protested against the move and more than 600 people have signed a petition calling for it to remain open.
"It's an essential component of village life. It's the reason why many of us moved to the village in the first place," said Jim Barratt, whose children have all been pupils at the school.
Hard-pressed councils have prompted anger in recent years by closing smaller schools in less heavily-populated areas to tackle surplus places.
"I would question the council's timing on all of this," said Mr Barratt.
"It's rather convenient that when the Welsh Government considers changing the school organisation code to include a presumption about closing rural schools, that our rural school, the only one recognised as rural in the Vale of Glamorgan, is now threatened with this so-called transfer to Rhoose, which is effectively a closure."
But the council defended the proposal and its timing, claiming it was the result of a consultation exercise and that it "does not constitute a school closure" under the Welsh Government's code.
"The council is proposing a £4m investment that would see Llancarfan Primary School move into a new state-of-the-art building as part of the council's 21st Century Schools programme," said council leader John Thomas.
"The consultation period has recently closed, and the council will now be carefully considering all the comments received before coming to a conclusion on the way forward."