Ongoing popularity of the established Woden school meant there was no sign of a let-up, according to Parents and Citizens president Karen Schilling, who said the ACT Education Directorate must offer the school extra space this year as a matter of urgency or risk losing frustrated families and potentially impacting on the school's top student education outcomes.

The Opposition, meanwhile, is putting pressure on Education Minister Shane Rattenbury to provide enrolment projections across the entire ACT over the next three years and explain how the government is going to deal with some clear cases of overcrowding – particularly in Gungahlin.

According to departmental figures, a number of relatively new schools in Gungahlin are already at capacity. Harrison's capacity is set at 1050, yet the February Census has enrolments at 1244.

Amaroo Primary has a capacity of 1075 and enrolments of 1060, while Gold Creek Primary has capacity of 525 and enrolments of 664 this year.

Ms Schilling said in the case of Garran, the last two years had put strain on the school as its 551 students lost flexible learning spaces for languages and science and "all available space is used to contain classes".

"We are a victim of our own success. People move into the suburb specifically because of the excellent school but we have no room to move," Ms Schilling said.

Garran has a total capacity of 550, but Ms Schilling noted that that was calculated on the maximum number of bodies a school could take. "Operational capacity" was 475 as it allowed for specialist classes and spaces to take place.

"We are really frustrated by the situation, and while the school has received quite some media coverage about it, we have yet to hear how it will be resolved."

Mr Rattenbury will visit the school next week to discuss the issue directly with the community.

Shadow Education Minister Steve Doszpot has been lobbying for the government to address chronic overcrowding for some time.

"It is not hysteria to suggest we are facing an impending crisis. And it is a crisis that could have been averted."

In April Mr Doszpot tabled a motion in the ACT Legislative Assembly calling on Mr Rattenbury to make public the directorate's enrolment projections for all government schools for 2017, 2018 and 2019, including identifying those that faced the most enrolment pressure.

Mr Doszpot also called on Mr Rattenbury to outline "how these issues will be managed so that parents across Canberra can plan with certainty for their children's future schooling needs".

Mr Rattenbury will make a formal response to the assembly in June.

Meanwhile, Mr Rattenbury said the long-standing issue of capacity enrolment at Garran was being addressed by not accepting out-of-area enrolments since 2015.

The school would also lose O'Malley as a priority enrolment area from 2017, with O'Malley joining Mawson Primary's priority enrolment catchment.

"I am aware of the capacity issues facing the successful and popular Garran Primary school, and the directorate is working with the school community to find solutions to ensure we are maintaining the best possible educational environment," he said.

"I will be meeting with the Garran Primary Parents and Citizens Association next week to hear from them directly about their concerns, and to discuss how we can work collaboratively to overcome them."

Mr Doszpot said the enrolment crush had been building for several years, noting that Chief Minister Andrew Barr ordered the closure of 23 schools when he was Education Minister in 2006.

He believed Labor had dropped the ball on enrolment provision as it "shuffled from one Education Minister to the next – four in seven years".

When asked about overcrowding last year, former Education Minister Joy Burch had "in each of our four networks school capacity will remain comfortably above projected enrolment growth".