Well, part of it is a longstanding belief - it's been in our...

Well, part of it is a longstanding belief - it's been in our education establishment at least since the 1930s - that somehow children should be allowed to discover knowledge for themselves, that they should construct their own knowledge. This has surfaced most recently in connection with mathematics instruction, where the idea is that they need to discover how to add for themselves. Rather than being taught how to add, they should construct this knowledge on their own.