Sam wants to be a teacher. He has been imitating the behavior, mannerism, and dressing style of teachers at his school. What group do the teachers that Sam imitates constitute for him?

Explanation:

The teachers that Sam imitates constitute  models   for him.

One of the first learning modes that every human use is the imitation. A baby can learn by direct experience (if he touches a metallic surface in winter the baby learns it is cold) or by imitation: when the baby sees the mom talking the baby learns to move the lips. The mother is baby's first model and the baby learns by imitating her.

When we grow up, we have many models: relatives, friends, peers, teachers, and virutally any person with whom we are in contact.

Imitating continues during all the life and teachers are very important models.

Specially, when the teacher is a good example and arouses admiration, the students will trend to imitate them. Particularly, in the case of Sam who wants to be a teacher: probably Sam has had some excellent teachers whom he admires and made him to want to follow their steps, which is why he imitates them. They are a good model to follow.