Students need to get feedback as they work. What specific feedback they need depends, of course, on exactly what they are doing and how they are doing it. Take two students who are learning biology by playing the part of a manager of a wildlife park. One might need guidance on how to balance short-term and long-term goals. Another might need details about what habitat herons prefer.
Schools tend to not be very good at giving students the feedback they need. Sometimes, the only feedback a student gets is a grade. When students do get feedback that has some content to it, it's typically because they get it during class discussion when all the students are getting the same feedback at the same time.
Where am I in the content of the book?