Pittwater High School deputy principal Brett Blaker is expected to take up the position next term.

The announcement comes as NSW government figures reveal year 11 and 12 students at the school have received hundreds of instances of minimum supervision due to a statewide teacher shortage.

The NSW government figures that were provided to parliament, show classes are being combined and students are often given only minimal supervision in schools in both country and city areas due to growing teacher shortages.

The figures showed that year 11 and 12 students have been left with minimal supervision more than 300 times this year at Canobolas Rural Technology High School .

At the same school year 7 to 10 classes have been merged more than 200 times.

There are also 11 permanent positions at the school, which are vacant and nine positions have been filled in a temporary capacity.

The information was revealed by the Minister for Education and Early Childhood Learning Sarah Mitchell in response to questions from Member of the Legislative Council Courtney Houssos.

"Minimal supervision does not mean students miss out on a lesson," Ms Mitchell said.

"Sometimes when casual teachers are unable to be sourced at the last minute, classes are merged to ensure continuity of education for students.

"Canobolas Rural Technology High School has been in a period of leadership transition in 2021. The current relieving principal commenced in April 2021 and will remain until the end of the 2021 year."

The other schools that were singled out were Murrumbidgee Regional High School in Griffith where a lack of teachers has left students under minimal supervision over 475 times this year; Concord High School in Sydney's inner west; Mary Brooksbank, a special school near Campbelltown; and Narrabri High School in the west.

NSW Teachers Federation president Angelo Gavrielatos said teachers are reporting class sizes of up to 45 students.

He said the Gallop Inquiry into the work of teachers warned in February that uncompetitive salaries and unsustainable workloads were contributing to the growing shortages of teachers.

"As we prepare for schools to go back next term, it is a stark reminder of why teacher shortages must be addressed as a matter of urgency," Mr Gavrielatos said.

"If we don't pay teachers what they are worth, we won't get the teachers we need.

"We know teachers face an enormous challenge meeting the needs of students after a long period of remote learning. We cannot afford to have shortages of teachers now and in the years ahead as we try and get all students back on track with their learning."

An Education Department spokesman said recruitment for the principal position has recently been finalised and confirmed the principal will start in term 4.

"Recruitment is underway for four vacant positions," the spokesman said.

"The department's School Recruitment and Placement team [has] worked closely with the school principal to fill permanent vacancies, and will continue to provide this support.

"Year 12 students have continued their studies with appropriate support."

The spokesman said the NSW government will also soon release a new Teacher Supply Strategy and Rural Incentives package, which will outline refreshed strategies to attract top quality teachers to regional parts of NSW.

The department is also trialling a casual supplementation program which looks at creating hub schools where casuals can be rapidly deployed to schools who need a casual teacher on short notice.

In the 2021/22 NSW Budget, the NSW government also committed $124.8 million for a Teacher Supply Strategy, due for release later this year.

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