In my 9th grade English class last year I had a high school student, we'll call "Sean", who was always interrupting. I could see that Sean needed attention. He's an only child of a single mother who works at a demanding job, so Sean is frequently on his own.
In class, I began asking him to help me present the lesson. If we were reading a play, I had him sit on a tall stool in front of the class and to read all the narrative parts. He's a good reader and a bit of a clown, so he did an excellent job. He was praised for his efforts and it seemed to help alleviate his tendency to interrupt the lesson, since he was now part of it.
His mother came to parents' night, and asked if I was having trouble with him because of his immaturity. I suggested to her, let him be a kid for a bit longer. He needs to work out something. If we make too much of his immaturity, it tends to reinforce itself. Praise him for times when he acts responsibly, but don't get too bent out of shape when he's immature, at least for now.
I don't have Sean this semester, but he stopped me the other day and said that the two semesters he spent in my class were some of his best experiences in high school. And, I am happy to report that he recently got some school-wide recognition for his athletic skills, which appears to make Sean act with more of the confidence of a young adult.
RWE