In our teaching training institute we teach our students behaviorism, cognitivism, social-constructivism and even connectivism as learning and knowledge theories (the first two say more something about how we learn, constructivism and connectivism tell more something about knowledge but are rather weak on how people learn). We don’t defend one theorie above the others. E.g. behaviorism works great for learning tables and other stuff we need to automatize, cognitivism has given us – even recently – great insights on how people learn, but also constructivism can have an impact on learning, even positive. E.g. if you look at problem based learning. For learning new stuff, a really bad idea (cfr Hattie), but when students do have the knowledge, the story changes. Also collaborative learning really can have a positive effect.
It’s a mistake to make constructivism the one and only paradigm you believe in, but luckily fewer and fewer people do this. As Brown 2012 has shown, in daily practice most teachers are rather eclectic.