My son has been watching Sal give lessons for the last year. Sal makes mistakes sometimes. My son usually notices and asks for clarification. We end up with a nice discussion about the topic at hand and arrive at a correct answer. If it's math related, I've got it covered. If it's not, we do some research.

Classroom teachers make mistakes. Textbooks make mistakes. But the system is set up to disallow question of these two authorities. Example: Math class is the first class of the day; teacher follows textbook and textbook is wrong; child questions and is waved off; is that kid gonna remember at the end of the day that she needed to ask mom about this problem? No.

I much prefer when Sal makes a mistake because it makes for a learning experience. What's nice is when my son comes back some time later and tells me that Sal's video has been corrected.