Most teachers understand the importance of using mistakes or errors as "teaching moments."

There is of course a danger of the student(s) making a mistake being the brunt of contempt or jokes. So, this needs to be handled very diplomatically.

However, there is another possible benefit of making a mistake. It can inadvertently point the project in another, even more fruitful direction. The teacher must then model for the students the flexibility of adjusting or modifying a project to accomodate the new direction.