Student groups and unions joined the picket lines at York University Monday, throwing their support behind thousands of teaching assistants and contract staff who are on strike for better job security.

The strike is on its fifth day as negotiations have halted between university officials and the members of CUPE 3903.

About 50,000 students are affected by the job action. CUPE 3903 represents 3,400 contract faculty members and teaching and graduate assistants.

"I've been getting a lot of support actually from unions at Concordia University as well," one picketer told CTV Toronto. "That was really nice too to see other provinces coming together to talk about this."

The strike began Thursday after union members rejected an offer from the university. CUPE chief negotiator Graham Potts accused management of "playing hardball" at the time. York spokesperson Alex Bilyk said the school had offered to go into binding arbitration.

The school's offer included a 9.25 per cent wage increase over three years, while the union is seeking 11 per cent over two years plus improved job security.

"Right now I have to apply for my job every year to nine different departments," Sharon Davidson, who has been teaching at the school for 15 years, told CTV Toronto last week. "I never know from year to year what I'm going to be teaching in those departments."

With a report from CTV Toronto's Galit Solomon