|"I am your father."|
How does this relate to IBL teaching? Before I started teaching via IBL, I primarily lectured. I thought I was getting through to students, but didn't really know until exam time. When I started teaching via IBL, then harsh reality slammed open the door. I realized what students didn't know, their misconceptions, how much logic was missing... It was quite the revelation.
It's in this stage, where I see a possible turning point. How we think about student learning affects our teaching decisions. The pathway I hope instructors take is to look at the situation, evaluate the learning issues, and then design tasks, assignments and classes to address the misconceptions. This is one of the values of informal assessment, and you get tons of it in an IBL class. You get info about where students are at, and then can take action to help students learn.
Another path I see taken is what is called the deficit model. The way this sounds is, "My students can't do this. They don't do that. They can't..." And it ends there. It's akin to the fixed mindset in teaching, where teachers view students' abilities as fixed, instead of malleable. In this path, it's the students' fault for not knowing, and the courses move on unimpeded.
Now I realize that this is an oversimplification, and students can fail or succeed for a variety of reasons. I want to get across a pragmatic point. When you use active-learning, you will get more info on how students think. This may be a surprise. An unwelcome surprise. The misconceptions have always been there, though, and the difference is that now you know what they are and can do something about it.
Instructors could (should) view these as opportunities, and do as much as they can within the limitations of their situation. The pragmatic viewpoint (and decidedly non-ideological viewpoint) is to help out as much as time allows. If an instructor has control over the syllabus and the course content (e.g. upper division courses), then there are more opportunities to deal with identified learning issues. If an instructor is teaching section 16 out of 30 of calculus, then there may be fewer chances. But there exists ways to carve out a bit of time to deal with the most pressing issues (such as making handouts, screen casting, and using small group work).
Feel the formative assessment, and inform your teaching it will!