It is certainly true that such knowledge is very likely to be remembered and understood, but it is not the case, as constructivists imply, that only such self-discovered knowledge will be reliably understood and remembered. This incorrect claim plays on an ambiguity between the technical and nontechnical use of the term "construct" in the psychological literature.
Many readers may not be interested in the technical details, but those who are may wish to know that the misleading ambiguity arose as follows.
Learning is closely associated with memory, since unrecalled experience cannot be said to be learned. For a long time it has been known that most memories are not just mechanical recollections but constructs built on a whole body of relevant prior experiences. (The constructed character of memory accounts for the unreliability of eye witnesses.)
Another example of the constructed character of knowledge is the understanding of language. The meaning of what we read or hear is not transferred directly from one person to another but is constructed by the listener, sometimes incorrectly.
Since memory and linguistic meaning constitute a lot of school learning, these two examples alone make plausible the idea that school learning is constructed. The misleading extension of the word to pedagogical method arises from the ambiguity between the idea that memories and word meanings are constructed and the idea that the only way to learn things properly is to construct or discover them for one's self rather than being told them. But since being told things is also a constructive, nonpassive process, the quasi-scientific claim that constructivism favors discovery learning is completely unfounded.
In fact, experience has shown that "discovery learning" (which see) is the least effective pedagogical method in the teacher's repertory. "Constructivism" is a good example of the way technical terms are sometimes used to give progressive ideas a spurious scientific-sounding authority. For example, some educationists distinguish between "endogenous" and "exogenous" constructivism. "Endogenous constructivism" is a mystifying term denoting learning that is self-induced by the student; "exogenous constructivism," by contrast, denotes learning that is induced from the outsider usually by the teacher. But note that behind the ponderous rhetoric lies the tacit admission that both discovery learning and guided learning are constructed. This means that, in the end, the term "constructivism" adds little or no illumination.
and Why We Don't Have Them.