The battle lines have been drawn between the Suid-Afrikaanse Onderwysersunie (SAOU) and the Gauteng department of education.
The two parties will meet in the Johannesburg labour court today.
SAOU has taken the department to court to compel it to repay and stop what it calls "unlawful deductions" from its members' salaries.
This after salaries of thousands of Gauteng teachers were docked in September and October after the month-long public service strike.
The union claims that the deductions were unlawful because their members downed chalk for a day only.
Chris Klopper, the SAOU's spokesman, said the union hoped that the court would stop "this unjustified practice".
"Some of our members who participated in the strike for a day had their pay deducted for a week and others more.
"It is unfair to do such a thing to teachers. They worked during the strike and deserve that money.
"We regret the implementation of such a drastic action because in the middle of October a settlement proposal was suggested to the department.
"Unfortunately they indicated that they preferred to deal with the matter in accordance with the strict legal procedure, which is why we decided to go the legal route," said Klopper.
Kate Bapela, the department's spokesman, confirmed that the union had served it with court papers.
"The department is willing to listen to what the union has to say. But the policy on the reimbursement of teachers' salaries deducted due to the public service strike stands.
"Teachers have to provide proof that they did not participate in the strike," said Bapela.
SAOU has also succeeded in obtaining similar orders against the department in KwaZulu-Natal and Limpopo provinces.