Recess time arrives. As students give you their papers give the work a quick glance and send students outside. Those papers that are basically correct put on the bottom of the stack. Students with unfinished papers send back to their seats. Those completed papers that indicate students are having trouble with the assignment put on the top of the stack.
Some students will still be sitting in their seats because they have not finished. Visit each student and evaluate the work. Papers of students who have everything right but are slow workers go to the bottom of the stack.
Those of students who are having trouble go on top. Dismiss students as you look at their paper.
You have now evaluated every student's paper. Throw away the good papers. Those students have the skill. Save the papers of struggling students. These students need further practice. You now know what you need to know. This takes five to ten minutes and holds students accountable for the work.