When schools had start teaching children that there are some problems that don’t have a correct answer. Stop giving them lists of questions, every single one of which has an answer, and there is an authority figure in the corner behind the teachers desk who knows all the answers.
And if you can’t find the answers you must be lazy or stupid.
When schools stop doing that all the time, I will admit that yes, it’s obvious that trial and error is a good thing.
Tim Harford: Trial, error and the God complex (http://www.ted.com/talks/tim_harford.html)