Last Friday, I was in Chicago, where the Chicago Teachers Union was staging a one-day strike. While the Milwaukee Public Schools, for which I teach, was on spring break last week, a number of my Milwaukee colleagues were marching alongside their Chicago brothers and sisters.

I wasn't; I was having a long-planned and much-needed vacation. Part of me felt guilty for not walking the streets with my fellow educators. Most of me, though, was glad to have some time not thinking about what has been a grueling school year here in Milwaukee, not thinking about what has happened to public schools here in Wisconsin, not thinking about what consequences will follow the April 5 elections and the Nov. 5 elections and on and on.

But I followed some of the run-up and aftermath on social media, including a series of thought-provoking tweets from Shaun Johnson, who writes the "@ The Chalkface" blog. He is an elementary school teacher in D.C., a former college professor and one of my current favorite teacher-bloggers.

"One day is certainly not the end of the world, but I'm not sure I support the CTU walk out from here in DC," he tweeted. "Teachers have already worked and will work numerous hours beyond what contracts stipulate. Why the walkout then?" In other words – if he'll forgive me the paraphrase – what lesson do you teach management by withholding labor you regularly already provide for free?

Johnson elaborated some on his blog later, including his distaste for calling teachers who remain in the classroom for the students (or, as he pointed out, for the sake of fellow employees who would not get paid for the day if school were called off) "scabs."

Striking or sick-outing as a teacher is a tricky business. I won't judge those striking in Chicago; their grievances are significant and real. For all that Wisconsin's teachers feel that they have been dumped on and maltreated in the last five years, what's happening to teachers in Chicago right now seems an order of magnitude worse. It deserves far wider attention than it's been getting.

Still, the counterpoint, as articulated by other Chicago teachers, hits my right in the gut. "Our profession has always cared about showing up for our children. Now isn't the time to stop." Though some of us got into teaching thinking we could change the world – and I did think that once! – we thought we would do so by working with the children: Those we teach will be the real change agents, and we teachers merely the ones holding open the door.

I couldn't help but think back five years to February 2011, when Wisconsin teachers, legally forbidden from striking, nonetheless called in sick for days at a time to go march in Madison to protest Act 10. MPS had to cancel school one day as a result; other districts lost more than that. While I did go to march in Madison, I did it on Saturdays after the initial round of weekday sick-outs had ended. Like my presence in Chicago over the weekend, this choice was more coincidental, as it turned out I was out of the country the week all that went down. I had already agonized over whether to leave my classroom and decided to go.

I had a supportive principal, a competent student teacher, some pretty self-motivated Advanced Placement students and an A/B-day schedule that meant even a week away was really only two or three days away from any one group of students I taught. Still, it took a pretty remarkable opportunity, and those specific mitigating circumstances, to convince me it was okay to be away from my classroom for a whole week. I had never done it before, and I have never done it since in nearly twenty years of teaching.

When I got back to U.S. soil, I wrote about exactly how hard a decision that kind of thing is and whether I would have been calling in sick like my colleagues. "I am not comfortable with the kind of labor actions that have shut down schools," I said. I wrote that while I was sitting in an airport and didn't really have the space or the iPhone-thumb dexterity to get deeply into it, but here's some of what I was thinking.

A whole lot of the students I teach get their most reliable meals at school. Where do they eat while I'm marching through the streets that day? Where do families find child care? How do parents who had to stay home with their children make up a day's missed wages? How do I tell a school principal I liked and trusted – and who, as I said, supported me – that though none of it was her fault I was going to be one of those teachers piling on problems for her. And like Johnson, I worried about non-teachers whose non-work day would be non-paid, too, from bus drivers to crossing guards to lunch ladies.

Mostly, I wondered what kind of teacher I would be if I chose to walk away from what was by far the most teachable moment in my students' lives.

A lot of students around the state, especially Milwaukee and Madison, made the trip to march with their teachers, which was undoubtedly a catalyzing moment for many of them who are now in college "feeling the Bern" or otherwise being the kind of activists we change-the-world teachers always hoped for.

Those who stayed, though, needed someone in the classroom who could help them understand the issues and figure out what this moment of revolt, if not revolution, was all about. And they wanted to know! They asked not just why school was canceled and why we marched, but why the other side felt it was important to change the rules about collective bargaining and health insurance and pensions (a related question I answered a lot: what's a pension?). And yes, I presented a variety of sides; I may be a flaming liberal online but try to be a neutral arbiter in the classroom.

The AP exam later that spring – remember my self-motivated AP students? – featured a question inspired by Thomas Paine, who wrote in 1791 that the young United States lived in "cordial unison," that Americans' "government is just ... and as there is nothing to render them wretched, there is nothing to engender riots and tumults."

I have rarely been more proud of my students than when they came to me that afternoon following the exam excited about how their answers had been deeply informed by what we discussed and read and watched and heard in class. For those kids, because I was in the classroom for them and used the Madison protests as way to get them writing and thinking critically, their answer to Paine was not grounded in dusty history but in a real and living present. That's powerful.

At the same time, it wouldn't have been possible for me and my students to even have that conversation without the actions of my colleagues who did throw caution and ambivalence and worry to the wind and went to Madison, without the college students and other activists – among whom number some of my good friends – who occupied the capitol for hundreds of hours straight.

In the end, if I were a Chicago teacher and not a Milwaukee one, I probably still come down where I was five years ago: I support the goal of their activism, but not walking away from their students.

I no longer labor under the naive belief that I am going to change the world. But I do remain firmly convinced that I can change some of my students, because I have seen it happen. I saw it happen in 2011. I saw it happen after Sept. 11. I saw it happen in 2008 after Barack Obama's historic campaign and victory. I bet a lot of Chicago teachers will see it this spring – but only if they are in the classroom.