Translation of "Diploma" in Japanese

Each boy has received his diploma.

男子生徒はめいめい卒業証書を受け取った。

Each student received his diploma in turn.

学生は各々順番に卒業証書を受け取った。

The principal presented each of the graduates with diploma.

校長は卒業生ひとりひとりに卒業証書を授与した。