In April, I went into a new class. I was separated from my best friend.
We will be put into new classes in April.
When I was at school, being separated into new classes was a big event.
自分が生徒であれば、こういう表現を使います:
go into a new class
be put into a new class
separated into new classes
例えば、
In April, I went into a new class. I was separated from my best friend.
(4月にクラス替えが行われた。私とベストフレンドが別けられた。)
We will be put into new classes in April.
(私たちは4月にクラス替えが行われる。)
When I was at school, being separated into new classes was a big event.
(学生時代はこのクラス替えが一大イベントでした)