Here's Dan Meyer blogging about a common teacher misconception: the supposed instructional value of allowing/encouraging students to struggle:
The good teacher knows if the learner learns through the ears, the eyes, or the hands just like the good spotter knows where the lifter wants support — at the wrists or under the elbows or on the bar. The good spotter is unhelpful; the good spotter doesn't intervene at the first sign of struggle but realizes that the struggle is essential, that the struggle is the entire reason they are there, and waits as long as possible before intervening.
The good teacher puts weight on the student's intellectual bar and lets her struggle under that weight as long as possible, asking questions to help her cut through the confusion, just like the spotter shouts encouragement at the lifter. (emphasis added)
I hate to ruin a colorful analogy, but the theory is wrong. Students struggling with material is not good for learning, retention, or motivation. Here's Engelmann on the topic:
Always place students appropriately for more rapid mastery progress. This fact contradicts the belief that students are placed appropriately in a sequence if they have to struggle—scratch their head, make false starts, sigh, frown, gut it out. According to one version of this belief, if there are no signs of hard work there is no evidence of learning. This belief does not place emphasis on the program and the teacher to make learning manageable but on the grit of the student to meet the “challenge.” In the traditional interpretation, much of the “homework” assigned to students (and their families) is motivated by this belief. The assumption seems to be that students will be strengthened if they are “challenged.”
This belief is flatly wrong. If students are placed appropriately, the work is relatively easy. Students tend to learn it without as much “struggle.” They tend to retain it better and they tend to apply it better, if they learn it with fewer mistakes.
The prevalence of this misconception about “effort” was illustrated by the field tryouts of the Spelling Mastery programs. Over half of the tryout teachers who field tested the first and second levels of Spelling Mastery with lower performers indicated on their summary forms that they thought the program was too easy for the children. Note that most of these teachers were not DI teachers and had never taught DI programs before. When asked about whether they had ever used a program that induced more skills in the same amount of time, all responded, “No.” Nearly all agreed that the lower performers had learned substantially more than similar children had in the past. When asked if students were bored with the program, all responded, “No.”
What led the teachers to believe that the programs were too easy? All cited the same evidence: students didn’t have to struggle. For them, it wasn’t appropriate instruction if it wasn’t difficult for the lower performers. (p. 17)
This is the danger for a would-be-profession that eschews empiricism in favor of individual intuition.