Chicago teachers held a second vote on September 21 to determine whether or not they will strike. The worker’s contract originally expired over a year ago, in June 2015. That December, teachers voted on a possible strike, and then participated in a one-day walkout in April. As of now, the union has not given Illinois any preliminary notice about an upcoming strike. Depending on the outcome of the vote, the earliest an open-ended strike could occur would be October.
See "Chicago Teachers Union Begins New Strike Authorization", CBS Chicago, September 22, 2016