Most of our activities have a built in control for error so that the children are able to know if they completed the activity correctly. This is important in a Montessori classroom because it supports the independence of the students as they complete their individual work time.
Here is an example of an activity with a control for error. This is a math activity where the children put the appropriate number of pom-poms in each basket. The colors of the paper in the baskets and making available only the exact number of pom-poms for each color serve as two controls for error.