Councils in Wales and England may have to pay for transporting pupils to schools in neighbouring authorities, following a landmark High Court case.
Three children from Ceredigion have won a legal battle to travel free on a school bus to Ysgol y Preseli, eight miles from their homes and just across the county border in Pembrokeshire.
Ceredigion had offered to bus them to its nearest Welsh-medium school, Dyffryn Teifi at Llandysul - 17 miles away - after Pembrokeshire stopped paying transport for out-of-county pupils attending its schools.
But Mr Justice Collins's decision means councils will have to pay for pupil transport to the nearest suitable school of their parents' choice, regardless of whether it is in their administrative areas.
Ceredigion has been granted leave to appeal and the case could be "leapfrogged" over the Court of Appeal to the House of Lords because of its significance.
The families' solicitor, Michael Imperato, of Cardiff-based Russell, Jones and Walker, said: "This is a victory for parental preference. The parents wanted their children to go to Preseli because they had older siblings there and it is a good school. No one had anything against Dyffryn Teifi, but it was twice as far away."
Cardigan high is the closest school to the homes of Byron Rees, 11, Matthew Jones, 12, and Aled Jones, 12, who are already pupils at Preseli. But no one had suggested this was suitable for them as it is English medium.
Mr Imperato added: "It doesn't matter whether the schools are English or Welsh speaking. This ruling could apply equally to a rural scenario in Cumbria, where children might go to a school across the border which is closer."
The dispute arose in July last year after Pembrokeshire council stopped free bus travel for Ceredigion pupils attending Ysgol y Preseli. Ceredigion refused to foot the bill for some of the affected children, saying they should switch to Dyffryn Teifi if they wanted free transport.
Mr Justice Collins said the case raised issues regarding the duties of local authorities to provide school transport to pupils who live more than the three-mile statutory walking distance away from their schools.