As I am not certain what part of the story your question reflects, I will provide an overview of Charlie's behavior as it changes throughout the book. At first, Charlie's relationship with Miss Kinnian is similar to that of a young elementary student with his teacher. He is eager to learn, despite his limitations, and seeks to please her with his attempts to master his studies. After his operation, however, things move in a different direction. With Miss Kinnian's help, Charlie's spelling and grammar improve and - gradually at first - he learns to read. Soon, his knowledge base exceeds that of Miss Kinnian, and he no longer needs her help as a teacher. Such gains lead him to realize a deep attraction for her, but because of his background, he is unable to act upon his feelings until much later. Tragically, Charlie's gains are short-lived, and by the end of the story he forgets he is no longer a student in Miss Kinnian's class, upsetting her when he shows up. But Charlie is not there to re-enroll or renew their relationship; rather, he has decided to move into a home for disabled adults.
I hope this helps - good luck with your studies.