From Education Week:
Whatever we call them, there are students who are ill served by grade-level curriculum—some because they have already mastered it, and others because they are far behind.
One recent study found that, across the United States, 95 percent of kindergartners tested in the fall demonstrated mastery of counting up to 10, identifying one-digit numbers, and recognizing geometric shapes. Despite this widespread level of proficiency, teachers reported spending an average of 12.7 days per month reteaching this content, a finding negatively associated with student learning.
American schools have long focused on remediation with the goal of ensuring that all students reach basic proficiency. But just as struggling children deserve resources to help them catch up, advanced learners also deserve differentiated programming if they are to grow.