Education Minister Caitriona Ruane is being challenged over the refusal to fund a bus service to NI's only post-primary Irish language school.
The governors at Colaiste Feirste in west Belfast are seeking to judicially review her department's decision.
The department would not financially back a pilot transport scheme for pupils coming from Downpatrick.
A judge was told such a service would encourage people to send their children and help increase the use of Irish.
Michael Lavery QC, appearing for the school's vice-chairperson, Colma McKee, said: "The more children that we can get to be educated through the medium of Irish the more you are achieving the objective which is the objective of the Good Friday Agreement and the statute."
The decision not to fund the service for 11 pupils who travel from Downpatrick to Colaiste Feirste was taken last September on the basis of an economic assessment.
But Mr Lavery claimed the department had failed to comply with a duty to provide suitable transport that would encourage Irish education.
Even though the school was said to be overcrowded while a planned expansion remains in limbo, the barrister contended that other pupils were being put off from going because of the travel difficulties.
Resisting the judicial review application, Tony McGleenan, for the department, described it as a "frontal assault" on a decision by the minister herself to reject a recommendation for a pilot bus service from Downpatrick.
Dr McGleenan argued that Ms Ruane has put the issue of transport assistance for Irish language schools to "the most anxious scrutiny".
He told the court she has received more than 25 written submissions from officials examining that specific problem.
"The sheer volume of analysis shows this minister's commitment to encouraging and facilitating the development of Irish language education in this jurisdiction," the barrister said.
He stressed how, despite her support, Ms Ruane remains constrained by laws.
Dr McGleenan added: "In this instance she could not commit public expenditure to a designated bus for the families of those children travelling from Downpatrick to Belfast.
"On fine analysis the minister was correct to do so, she has properly applied the statutory framework, and notwithstanding her general support for development of Irish language medium education the decision she reached was correct in law."
The hearing continues.