Stuttering: An Iceberg

In many ways stuttering is a lot like an iceberg: The visible part of the
iceberg, which is at the top, represents the physical struggle of
stuttering, while the much greater part lurks unseen in the ocean. This
is known as the "emotional baggage" which is also very important.
The shape, density, size and hardness of the iceberg varies a lot, just
like the stuttering type and condition of various people. That's why you
need a therapist to help you alone. I do not think classroom therapy is
good enough.
You can learn more about the iceberg analogy of stuttering here.