By Chris Tye

CHICAGO (CBS) — Tens of thousands of teachers out of classrooms on Thursday, and many of them marched in the Loop.

CBS 2’s Chris Tye spoke to some of them about their need to march and have their demands met by the city.

As those demands are concerned, most know the sticking points on salary and support staff.

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But the trickier question that stumped even the teachers: class sizes.

Like thousands of her striking brothers and sisters, Miriam Ruiz knows every day away from the classroom compounds the stress on families and the trickle down effects on education and athletics.

“This is extremely difficult for us,” Ruiz said.

When CBS 2 asked a handful of these teachers what their demands are on class size, let’s just say most didn’t pass.

The union is calling for a primary school class size reduction, from 28 to 24 students. In high school it would slide from 31 to 28 students max. And unlike passed contracts, this would be enforceable.

Few answered it properly, like teacher Tricia Chmielinski

“I know that we were asking for 24-28 max, which I think is reasonable,” she said.