Is learning always observable?

I believe teaching is a sacrifice.  The strategies used by the teacher are very
important not only to teach, but to find out the learning too.  So, a good
teacher can find many ways to understand if learning has happened. .  She can
breaking off the students into partners or small groups to discuss what they
learned; she can give them the time to exchange the ideas and to prepare the
answer of the questions.

But, a good teacher should also connect to the pre-knowledge of the students. I
believe a formative evaluation keep students and the teacher informed of
student’s progress toward learning the subjects. It provides teacher with
valuable information. It can help teachers understand the degree to which
students are learning the course material and the level of their knowledge. But,
the formative evaluation is not the only way to understand the level of learning
of the students. Preparation, assessment, assignment and reflection can help the
teacher to know much more the students; and, certainly, the teacher should give
the feedback and encourage students to participate actively in their own
learning .