Daniel Garcia was supposed to spend Christmas with his girlfriend and her family, even staying overnight at their home so he wouldn't be alone on the holidays.
Instead, the 18-year-old Toronto student has spent the past few days in an immigration detention centre after police arrested him Thursday night, according to his friends.
Mr. Garcia faces deportation to Mexico and could be sent away as soon as next week, they said.
"It makes me so sad because if he gets deported, I never will see him again," his girlfriend, Martina K., told the Canadian Press on Saturday.
She asked not to be identified by her full name since her immigration status is also not certain.
Dozens of students, teachers and community workers set aside their own Christmas plans on Saturday to defend Mr. Garcia, described as an exemplary student and a caring friend.
They gathered in a church to call on the federal government to allow Mr. Garcia to stay in Canada and have the courts review his case.
Many said they worry Mr. Garcia will be quietly deported during the holidays, before he has a chance to appeal the decision.
The government "has a nasty habit of enforcing deportation orders around Christmas time when they know people can't access the courts," said Karin Baqi, a lawyer who has spoken to Mr. Garcia since his arrest.
"We want to make sure he doesn't get removed in the cover of the night."
One of Mr. Garcia's teachers, Hillel Heinstein, said the teen is particularly vulnerable because he hasn't been able to get proper legal assistance.
Mr. Heinstein said Garcia's deportation would be "a tremendous blow" to the school and to the community.
Ms. Baqi, the lawyer, said the teen's pre-removal risk assessment was filled out incorrectly after his previous lawyer died.
Mr. Garcia, a student at Parkdale Collegiate Institute, arrived from Mexico with his sister in 2007. Both filed for refugee status, saying they faced persecution and death in their homeland.
The refugee claim was rejected and Mr. Garcia submitted an application for a pre-removal risk assessment, which evaluates the danger the person will face if deported.
Mr. Garcia said in a statement he hadn't received a decision on the application when he was stopped by police and turned over to immigration officers on Thursday.
The student says officials told him they mailed him a decision months ago.
"He's obviously very afraid of what could happen if he goes back to Mexico," Ms. Baqi said.
Mr. Garcia's sister is also in detention and could be deported as soon as Monday, Ms. Baqi said.