Quebec's new secularism law is creating situations that "darken the climate of a school," says the head of a union representing Montreal teachers.

She says the law is compelling school boards to turn away teachers as they're facing a labour shortage.

"I understand some people living in this type of climate are thinking about whether they want to stay in public schools," said Catherine Beauvais-St-Pierre, president of the Alliance des professeures et professeurs de Montréal.

The law, which bans some public servants in positions of authority from wearing religious symbols at work, has been creating confusion in the public education system.

New teachers are banned from wearing symbols such as a hijab, turban or kippa under the law. Those already on the job are exempt under a grandfather clause, as long as the remain in the same position.

"We're learning how it's going to be managed with what's happening now. We weren't given any details about how to manage this law," Beauvais-St-Pierre said.

Beauvais-St-Pierre was speaking in reference to a newly hired teacher at Quebec's largest school board who has been told to remove her hijab — or stop teaching.

The Comission scolaire de Montréal (CSDM) confirmed it sent an elementary school teacher a warning about her hijab last month.

The school board would provide no other details.

CBC News was unable to speak with the teacher directly, but a spokesperson from the union said she's "shaken."

Last year, she was working as a substitute teacher with another school board while she finished her teaching degree, the union spokesperson said.

If she had stayed with that employer, she would have been allowed to keep wearing her hijab due to a grandfather clause in the law that protects teachers who had been wearing a religious symbol on the job before it passed.

But since she was hired by a different board, she lost that right. The teacher's first day at work would be Tuesday.

Catherine Beauvais-St-Pierre says teachers are in short supply, and that the law further limits the pool of candidates for the public system. (Radio-Canada)

"[The law] opens a door to certain consequences," Beauvais-St-Pierre said. "When we teach, there's an openness. We teach about how to live in a society."

She said it's going to take some time before all the effects that the law has on the education sector will be known, and that the sector will have to learn how to manage each type of case as they come.

"In the meantime, we're low on teachers — and teachers are exhausted," Beauvais-St-Pierre said.

She added it's likely that teachers who are affected by the law will switch to the private school system, where the law doesn't apply.

'The law is the law,' education minister says

The CSDM, along with other school boards such as the English Montreal School Board and Lester B. Pearson School Board, was initially against the bill.

But since it passed on June 16, school boards say they have no choice but to enforce the secularism law.

"It's not a surprise," said Education Minister Jean-François Roberge when asked about the CSDM teacher's situation.

"The law is the law, and we will apply the law. Each school board has the obligation to apply the law."

The teacher could be further sanctioned if she doesn't co-operate, but what her punishment would be is unclear.

Roberge said if she wants to avoid punishment, she also has the option to remove her hijab at work.

As the school year begins, other school boards are taking measures to enforce the law.

Two people were not hired by the Commission scolaire de la Pointe-de-l'Île (CSPI) this school after being informed of the law by the school board and refused to remove their religious symbols.

"We're simply respecting the law," said CSPI president Miville Boudreault.