If you've done some research to see what the Montessori Curriculum and Methodology is all about, then you've probably come across the term "Control of Error" many times!
Plainly speaking: it is an aspect built into many Montessori Learning Materials that enables the preschool child to check the accuracy of their work without the assistance from an adult or peer.
Let's use the Math Lesson picture above as an example for explaining the Control of Error. To understand how the Control of Error works, we need to understand the Purpose of this Lesson; what is it's goal for the student.
Prior to working with this lesson, children need to have already Mastered their understanding of the concept "Zero", be able to recognize numbers 0-9, and understand that each number consists of the correct amount of "objects".
For this Lesson, the child first spreads their red wooden numerals 0-9 on the bottom of their work space. Then they begin at the number "zero", and add the correct number of wooden counters (in this photo, wooden ladybugs) above it. Then then move on to the "two", and place the correct number above that red number. They repeat this action all the way to "nine".
As we said, in Montessori almost every lesson has a built-in "control of error"; and that the control of error is a way for the child to self-check their work to see if they performed it correctly.
With this specific material, the child will know they placed all the ladbugs in the correct places if they have none left over when they are finished - and if they have some remaining unused, they can see for themselves there is an error somewhere.
This is key - by seeing and recognizing there is an error SOMEWHERE, the child then learns to go back and check their work - it isn't a adult informing them of a potential mistake, or telling them how to fix it - it is the child himself. That concept is the foundation for a child learning they have the ability to learn independently.
Then they can re-check their work (by starting back at "zero" and counting each line's total ladybug) until they find the error.
This Control of Error is a key part of the Montessori Method, as the philosophy teaches that children learn much more intrinsically, and are more advanced in their true understanding of the various concepts if they are taught how to check their own accuracy of their work - in short, that they do not need to rely on an adult to give them this feedback information. They are able to become self-directed, self-motivated learners!
And MANY key early learning studies have shown that children learn more when they have these skills, as well as translates into a true love of learning!