Set theory in the 4th grade ... It made perfect sense to me. I used to blurt out the correct answers without raising my hand. The other kids hated me for it, and the teacher told me to shut up.
UMM was a failure because it seemed to rely on an "intuitive" approach to maths - it seemed to be expected that everyone already knew the subject, and that all that was necessary was to present the material and the students would automatically "get it".
AFAIK, only one in seventy did, and the teachers already thought of that kid as a problem child.

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