While we want to provide personalized attention, especially to submitted work, testing and grading, learning is still heavily dependent on the teacher. But because the teacher in turn is responsible for assembling, and often presenting, the materials to be learned, customization and personalization have not been practical. So we have adopted a model where small groups of people form a cohort, thus allowing the teacher to present the same material to more than one person at a time, while offering individualized interaction and assessment.