not water in a sieve

Knowledge must result from the activity of the pupil's own mind. Along with acquiring knowledge with the aid of the teacher, he can also acquire knowledge by applying his mind by which he knows the first principles of all knowledge. The teacher often points out issues which the pupil had not thought of and shows the relationship between concepts which the pupil would not have noticed without the teacher pointing them out. Aquinas stresses that teachers are only for helping the student know. The student must digest the knowledge. Otherwise, it is like pouring water into a sieve.

Educational Theory of Thomas Aquinas