I want to create a discussion about tracing the different reasons for “stupidity” of a student/schoolchild/learner. By this term I understand persistently low performance. I will start with my ideas and observations and expect you to share yours and give comments to mine.
Very often teachers relate stupidity to low IQ, or brain functioning. However, it may have psychological origin as well. It may also be a self-reinforcing phenomenon. Consider the case when a timid pupil with average IQ comes to a class but misses something, and authoritarian teacher presents him as a stupid, and later class starts laughing at him, so that he loses interest for studying and performs even lower. I read a book about an experience of private teacher in mathematics who found different pupils to be locked at some level of school program. She was able to help many of them with an individual approach.
But stupidity can also occur even with experienced teachers if they start some other studies not in young age. For example, learning a foreign language is much easier at young age, because the ability to memorize unknown words has a tendency to decrease with age.
Some older people can never learn how to use computer or mobile phone. Young children can use a completely different scheme for that based maybe on some memory of fingers where to click. They also cannot explain this rationally to older generation, because this skill comes at early age. On the other hand, books about software are too long and detailed to be read and used by the majority of people. Here we have especially hard problem for the beginners.