From Wikipedia on John Holt’s book:
When children are very young, they have natural curiosity about the world, trying diligently to figure out what is real. As they become “producers”, rather than “thinkers”, they fall away from exploration and start fishing for the right answers with little thought. They believe they must always be right, so they quickly forget mistakes and how these mistakes were made. They believe that the only good response from the teacher is “yes”, and that a “no” is defeat.
They fear wrong answers and shy away from challenges because they may not have the right answer. This fear, which rules them in the school setting, does their thinking and learning a great disservice. A teacher’s job is to help them overcome their fears of failure and explore the problem for real learning. So often, teachers are doing the opposite — building children’s fears up to monumental proportions. Children need to see that failure is honorable, and that it helps them construct meaning. It should not be seen as humiliating, but as a step to real learning. Being afraid of mistakes, they never try to understand their own mistakes and cannot and will not try to understand when their thinking is faulty. Adding to children’s fear in school is corporal punishment and humiliation, both of which can scare children into right/wrong thinking and away from their natural exploratory thinking.
Holt maintains that when teachers praise students, they rob them of the joy of discovering truth for themselves. They should be aiding them by guiding them to explore and learn as their interests move them. In mathematics, children learn algorithms, but when faced with problems with Cuisenaire rods, they cannot apply their learning to real situations. Their learning is superficial in that they can sometimes spit out the algorithm when faced with a problem on paper, but have no understanding of how or why the algorithm works and no deep understanding about numbers.