Ramona Jennex said the job cuts are a recognition that the ratio of teachers to students was lopsided.
"We're in the position of looking at making sure our resources match the number of students in our system," she said.
Jennex said schools in the city have seen a 4.2 per cent decline in enrolment over the last three years, adding that all of the cuts are being done through attrition.
But Liberal Leader Stephen McNeil said the school board has indicated that only 25 of the eliminated positions were as a result of declining enrolment for the upcoming school year.
He said taking teachers out of the classrooms would make it even harder "to deliver the kind of quality program that we believe in, that our children deserve and they expect."
Progressive Conservative Leader Jamie Baillie said class sizes will ultimately go up as a result of the cuts.
"The quality of education is going to go down," he said. "It should be the first priority of the government to protect the quality of education in our classrooms and they have failed to do that."
Jennex said she believes school boards have done a good job of ensuring that cuts are not affecting the quality of classroom instruction.
On Wednesday, the board said it eliminated the positions to deal with a $3.2-million decrease in funding from the province and expected to save $7.6 million in 2012-13 as a result of the cuts.
In a statement, the Canadian Union of Public Employees said cuts announced in Halifax and within other school districts in the province go too far.
Danny Cavanagh, president of CUPE Nova Scotia, called for a review of the province's education system.
"At the risk of stating the obvious, the current funding formula simply is not working," he said.