CHICAGO (CBS) — The decision for the Chicago Teachers Union to vote on whether or not to strike comes on a day when both sides sat down to the negotiating table, with no change or new proposals being offered to teachers, CBS 2’s Dana Kozlov learned. However, they’ll continue to meet more than once a week, while teachers continue to prepare for a possible strike.

CTU is bolstering its resolve, weeks before educators might walk off the job. Even though the union took a strike authorization vote last December, giving the OK, CTU President Karen Lewis says members will take another one this month, this time, by signing petitions, instead of a secret ballot.

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“We want to make sure our t’s are crossed,” Lewis says.

Teachers have gone 15 months without a contract, rejecting a negotiated deal last winter, and balking at a fact-finders recommendation last spring.

In both, all teachers would get an 8.75 percent raise over four years. But teachers getting step and lane increases would actually get a 13.5 percent raise, on average.

At the same time, teachers would be asked to contribute 10.5 percent more to their pension.

In the end, a gain for some, but not all.

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“It’s their pension they’re going to pay into that they themselves and their families will get; and we’ve asked the public to step forward, but we’ll also do it in a way that respects them.” Chicago Mayor Rahm Emanuel says.

A CPS Spokesperson says, “A strike can be averted, and CPS will work tirelessly to make sure children’s education and progress is not interrupted.”

But Karen Lewis isn’t so sure.

“We’ll do it if we have to, to set a date, to set a strike date,” Lewis says.

The CTU is required to give CPS at least 10 calendar days notice before teachers walk.

Strike preparation workshops for teachers are taking place next week.

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A CPS spokesperson says officials are open and willing to listen to any ideas offered by the union to keep teachers in class.