Data released by the state government on Thursday included details of enrolment figures for senior secondary students across the state.

Education Minister Jeremy Rockliff announced a $30 million election promise this year to upgrade all state schools to grade 11 and 12 by 2022 to improve retention rates.

However, the data released this week shows the bulk of the North’s grade 11 students were still at the region’s two colleges – Newstead College and Launceston College.

Launceston College has 677 students and Newstead College has 298 grade 12 students.

Nine northern schools featured in the data release, including Campbell Town District High School, Cressy District High School, Deloraine High School, Flinders Island District High School, Launceston Big Picture School, Lilydale District School, Port Dalrymple School, Scottsdale High School and St Helens District High.

Scottsdale High School transitioned to offering grade 11 and 12 in 2015, but the recent data shows it only has 17 grade 12 students in 2018. Scottsdale had 298 enrolments in 2018, and 289 in 2017.

However, Scottsdale has the most grade 12 students than any of the other nine Northern schools.

At the other end of the scale, Cressy District High School had only three grade 12s in 2018.

The school had 303 enrolments for 2018 and it extended to grade 11 and 12 in 2017.

Enrolments for the nine schools featured in the data was a total of 2614 for 2018.

Statewide figures show there 28 students at Smithton High School, in the state’s far North-West, and 36 at Sorell School, in the South. Elizabeth College, in Hobart had 514 grade 12 students.

The South has a total of 144 grade 12 students at extension high schools. The North-West has a total of 137 high school grade 12s. The figures don’t include college enrolments in the North-West or South.

Extension schools were discussed during budget estimates last week, with Launceston MLC Rosemary Armitage asking Mr Rockliff about student numbers in Launceston.

“What we are doing is providing the opportunity for students to continue to use 11 and 12 from grade 10 who otherwise might not have gone onto college for a variety of reasons.  There are a number of barriers to prevent students or depending on the student and the student's situation as to why they would not go into one of the eight colleges around Tasmania,” Mr Rockliff said.

However, Labor's Michelle O’Byrne said the data showed there was a need to assess the full impact of the extension program.

“We have always supported the programs where distance is truly a barrier for participation,” she said.

“However before we push every school into year 11 and 12, we really need to understand the impact of what we are doing to ensure we are doing what is best for our students."

"To do that we have to analyse their engagement. What is working well and what is not working ... are we actually improving their outcomes?”

Tasmanian Association of State Schools Organisation operations manager Deborah McOrist-Mitchell echoed the concerns raised by Ms O’Byrne.

“We are grateful the students are in schools, we understand the barriers but we don’t agree with it if it at the expense of our college system,” she said.

Ms McOrist-Mitchell said TASSO had been calling for the past one or two years for the state government to stop its roll out of extension high schools and do a full review of enrolments.

She said while they supported the roll out in rural areas, but also not at the expense of financial assistance for rural students if they wish to access transport and accommodation assistance to attend an urban college.

“The Hodgman Liberal Government continues to release this data, in the interests of openness and transparency unlike our secretive predecessors because we believe it encourages engagement and discussion between the government and the Tasmanian community,” Mr Rockliff said on Thursday, in response to the data release.