Sold on the Education Directorate website as "providing certainty" to NSW families, the changes mean students from NSW can now only attend certain schools in Belconnen and Tuggeranong, billed as pathway schools.

The changes come as schools in more popular zones - including in Gungahlin, the inner south and the inner north - grapple with capacity issues.

Families in Yass, Bywong, Collector, Goulburn, Harden and Murrumbateman are among those who can now send their children only to Evatt, Florey and Charnwood-Dunlop primary schools, Melba Copland Secondary School, UC Kaleen High and Lake Ginninderra College.

Even then there are set pathways, including, for example, that students who enrol in a Canberra primary school can now only attend Melba Copland Secondary School through high school and college.

Children in Braidwood, Bungendore, Jerrabomberra, Michalego and Queanbeyan can attend Gilmore, Calwell and Richardson primary schools, Wanniassa School, Caroline Chisholm School, Lake Tuggeranong College or Erindale College, and again must follow a prescribed course depending on where they first enrolled.

NSW families with a child already attending an ACT school may not be able to enrol that child's sibling in the same school, depending on enrolment pressures.

Children now in non-pathway schools will only be able to attend prescribed pathway schools when transitioning from primary to high school or high school to college.

They can continue to attend their current school until transition, the directorate assured. NSW children participating in ACT special education programs will not be affected by the decision.

About 4500 ACT students live in NSW, about 1800 of whom attend public schools. The figure is expected to grow thanks to large residential developments close to the border.

"Previously, NSW families wishing to enrol their child were required to apply for a place in a Canberra public school and applications were considered only after all applications by ACT residents were processed, and then only by schools with enough capacity to accept cross-border applications," the education directorate website said.

"Many families were unable to receive confirmation of enrolment until close to the start of term one.

"Due to significant growth in enrolments in the ACT, the number of Canberra public schools able to accept students from outside their priority enrolment area (including from NSW) has reduced and this trend is expected to continue.

"Monitoring the progress of NSW enrolments indicates that there are increasing numbers waiting for responses from schools that are filling with ACT students. As a result, we are taking this proactive step to streamline and fast track processes for NSW families."

Murrumbateman families have been campaigning for a local school for about five years. Mike Reid, a key voice in the push for a local school, said there were about 500 primary school-aged children who travelled to Yass or Canberra from Murrumbateman each day.

Taking away school choice would have a negative impact on parents travelling to Canberra who had chosen the school closest to their workplace, he said.

"To send them in the opposite direction [to Yass] then going to work in Canberra is silly," Mr Reid said.

Yass Valley mayor Rowena Abbey said the decision had taken the council by surprise.

"At this time we are unaware of what consultation was conducted and how residents affected have been told about these changes, or even when they will take effect," Cr Abbey said.

"The feedback that councillors are receiving from the community is about the lack of choice, with only three primary schools and one high school available to Yass Valley students as well as the ongoing concern over siblings being forced to attend different schools, which only adds costs and logistics to families."

The decision was made in consultation with the NSW government during discussions held under the 2016-2017 ACT-NSW Memorandum of Understanding for Regional Collaboration.

Do you know more? Contact emily.baker@fairfaxmedia.com.au.