To finish or not to finish

Different teaching styles exist because different learning styles exist. Everyone works at different paces. However, a persistent problem I have noticed in pretty much every class is there are no alternative options for students who finish their work before others. Often in these cases, boredom can be misconstrued for being unfocused, when it's actually just the opposite. These kids should be rewarded, not just made to sit there doing nothing. Also, I think some students are slow just to give themselves something to do, because even doing a stupid old worksheet is better than sitting there twiddling your thumbs. But more often than not, especially in remedial classes, teachers do not provide alternative activities for students who have finished. In grad school, these were called "anchoring activities," literally for anchoring students in their chairs until the bell. They are also supposed to provide enrichment on the same skill set, thus anchoring the students' knowledge. But in many classes I have seen here, different pacing does not seem to be an issue when it comes to lesson plans, even though it is a specific tenet of proper differentiation, which, in every interview I've ever been to, is the most important technique in teaching. I wish I could get more practice with experiencing it in action.