in my opinion u didn't have the right to send him out of the class. you could have warned him, send him to the director or even talk with his parents.
if he is done with his work he has every right to do whatever he wants aslong as he's not involving others who havent done their work yet.
teachers in ethiopia want to be THE BOSS of students and it's not right.
if it was my child that you send oud of the class i would be pissed.
plus why would a student stand up greet the teacher??? they arent his parent.
i'm so happy that things have changed in ethiopia these days, couse in my time we student were treated like dogs by the teachers.