Teachers at Assumption College have continued to wear black ribbons to classes in a protest for pay rises and against a cut in allowances.
The college closed for five days late last month after the teachers demanded more pay and fought against the previous college director's plan to merge the primary and secondary campuses.
Although the St Gabriel Foundation, which oversees Assumption College, has replaced college director, Brother Anant Prichavudhi, tensions remain high.
Brother Anant's plan to merge the two campuses has been scrapped because the college administrators failed to submit the required documents to the Office of the Private Education Commission (Opec) by the Jan 31 deadline.
Teachers say the pay issue has not been settled.
"We still wear black ribbons as a symbol of protest to urge the new director to swiftly solve the problem," said a teacher at the college's secondary school campus who declined to be named.
Every teacher's salary should have been increased in January 2012, but the pay rises have been delayed, he said.
The college has also stopped paying professional fees and living allowances to teachers.
It is believed the school delayed the pay rise and scrapped the other payments because it spent 2.5 billion baht to build a new campus for its English-language programme on Rama II Road.
"Parents donate to the school for the development of their children's education, so it is unfair the money is spent for other purposes," the teacher said.
"We are also worried the school might not have money to pay the teachers."
He claimed the college was supposed to increase the salary for each teacher holding a master's degree to 50,000 baht at the beginning of last year.
Teachers with a bachelor's degree were to have their pay increased to 30,000 baht, he said.
He said teachers also disagreed with the plan to merge the campuses because they feared some of the teachers at the primary school would lose their jobs.
If the campuses were merged, all teachers from the primary campus would have to be transferred and reappointed as teachers at the secondary campus. That appointment would require a teaching certificate under the Education Act.
"Some of them do not have the teaching certificate, but they have worked for the school for several decades," he said.
The merger problem, however, has ended because the college failed to meet the Jan 31 deadline to submit the necessary documents to Opec, he said.
The new director has not discussed the pay rise in detail with the teachers, he said.
He said the college's teaching staff would be more cautious in taking any new steps to push for their pay rise demands because they did not want students and the college's reputation to be affected.
Chanwit Tabsuphan, Opec's acting secretary-general, said Assumption College was among 600 private schools which receive no financial subsidy from the government.
The school is permitted to collect higher tuition fees and Opec has no power to force the administration to increase teachers' pay, he said.