How do I send a message to just one group?

In Messages, choose the group under To instead of Whole school.

1. Open Messages.
2. Under To, tap the group you want (you can tap several). Whole school is deselected.
3. Write the Subject (at most 150 characters) and the Message (at most 5,000 characters, plain text).
4. Tap Preview, then Send by email.

Only the active students of the group or groups receive the message, one address per family. To write to everyone, tap Whole school. Instructors have access to Messages only if the owner allowed it.