Enable the Group Page Access Setting
  1. Navigate to Core >  Security > Select Group Page Access
  2. Select Activities 
  3. Filter on the 2018-2019 Year for Middle School
  4. Select Add Access
  5. Include the following roles: Leaders of Activites
  6. Enter in the preferred access dates for those users

This would then allow the teacher the ability to access this group through their faculty persona.

Add the Events (teacher will do this)
  1. Go to their faculty persona
  2. Groups > Select the preferred Group
  3. Select  Bulletin Board> Select Enter Edit Mode
  4. Drag the Events Widget onto the bulletin board
  5. Select Add
  6. Enter in the preferred info for the event > Select Save
  7. Select the option to Publish the Changes in the left corner of the screen