How does hypnopaedia represent social control?

Hypnopaedia is the principle of sleep teaching. It represents social control because it is used to condition all of the children. The Director explains that while hypnopaedia is not useful for imparting knowledge, it is useful for what is called "moral education," or conditioning the children to be happiest in the caste to which they were born. For example, we overhear a group of sleeping Beta children listening to a tape that plays over and over telling them that they don't want to play with Delta or Epsilon children and, further, telling them that should be glad to be Betas. They are also told they are lucky not to be Alphas, because Alphas have to work too hard. All the children who are not Betas listen to tapes that similarly tell them to be happy with their own caste. Today, we would call this brainwashing.