Great is truth but still greater from a practical point of view is silence about truth. By simply not mentioning certain subjects... totalitarian propagandists have influenced opinion much more effectively than they could have by the most eloquent denunciations.
The denunciation of the young is a necessary part of the hygiene of older people and greatly assists the circulation of the blood.
In the ideal classroom the teacher is either spending all of their time doing deep interventions with students on a one-on-one basis or facilitating true interactivity - labs simulations projects.