Within the last year, a School of the Arts (Sota) student has seen three of her teachers leave the school.

First, it was a senior teacher in the literature department. Then another literature teacher, also a senior teacher, left last month. Two weeks ago, she was told that her biology teacher will leave early next month - five months before the International Baccalaureate exams.

She and other students in her year told The Sunday Times they are worried about the impact such departures will have on their learning.

Some students also have seen their coursework supervisors leave halfway through the year. Internally assessed coursework such as study reports make up 20 per cent to 50 per cent of overall grades.

"The change from one teacher to another has been very abrupt," said the final-year student, on condition of anonymity.

The issue of staff attrition at Sota came under the spotlight after a student's art piece sparked discussion.

Year 6 student Calleen Koh, 18, sat down in front of the staffroom door and wrote down the names of teachers who had left on at least 20 pieces of paper, which were then folded into aeroplanes and placed outside the general office. The school removed the planes, explaining that they were put up without any explanation and went against guidelines.

Sota said 10 full-time teachers, or about 6 per cent of its teaching staff, left the school in the first two terms of this year. The school will fill all vacancies by the end of next month, when the third term begins.

The Sunday Times understands that at least six who left this year were in senior positions such as senior teachers or heads of department. Sota said that staff who resign have to give a minimum notice period of one month.

It is understood that on May 19, principal Lim Geok Cheng addressed the removal of the art piece, and congratulated Calleen on her work, in a speech to the school. Ms Lim also said that it raised questions about why teachers are leaving.

She explained that the perception that a large number of teachers are leaving the school at the same time may be due to there being popular windows when teachers choose to leave, such as after they collect their performance bonus or to time it with the June holidays.

Sota had said earlier that turnover rates at the school have remained constant at 12 per cent over the past five years, and that teachers may leave because of a move overseas, new job offers or the end of their secondment from the Ministry of Education. As Sota is an independent school, around nine in 10 of its teachers are direct hires.

Several current and former teachers said there may be other possible push factors. One teacher, who had been with Sota for more than five years, said that his "best years in teaching" were spent there. Yet he left sometime in the last three years as he was worried the school was more focused on attracting academically bright students instead of those with a bigger interest in the arts. "The attraction for any student coming into Sota must be the offer of an arts education experience unlike other schools," he said.

But he noted that such a disagreement "can happen in any organisation", and said that the school does not lack good teachers who are "passionate about teaching in Sota".

Another teacher who left said she did so to pursue another job. But she said disagreements with new heads that were appointed in her department in the first half of 2015 also prompted her departure. "They don't quite understand what it means for literature to flourish in an open-minded and critical climate," she said.

For example, an exam piece including an account by someone who had gone through the 1980s Aids crisis in the United States was met with " very unnecessary resistance", though it was ultimately given the go-ahead.

A current teacher said that some of her colleagues were unhappy with the amount of micro-managing by their superiors.

Madam Connie Looi, 50, a parent of a Year 4 Sota student, was initially concerned about how the staff departures may affect her daughter's studies, but felt more at ease after she spoke to the Sota parents' association about the issue.

A parent of a Year 6 student, who declined to be named, is worried about her daughter, who has started to fail some subjects. "When teachers keep changing, how can they monitor her performance and give her feedback?"

Ms Lim said that new teachers are paired with another teacher in a similar job scope to help them settle. The school also makes immediate arrangements when a teacher wants to leave to minimise disruption. "We are appreciative that our teachers stand together whenever needed, for instance, volunteering to take on more teaching hours."

As for criticism of the removal of the paper planes, Ms Lim said that Calleen "is most welcome to request to have her work presented again".

Mr Sean Tobin, head of the theatre faculty, said that Sota is still learning how to handle delicate situations such as the incident involving Calleen's art piece.

"There are no easy answers to questions about how to maintain harmony while also encouraging experimentation and discovery."