I work at a school and I am trying to configure email auto parsing but not winning!

We have 2 technicians, 1 for primary school and 1 for high school. Also a maintenance manager. I have set up 3 Support Groups - PrimarySchool, HighSchool and Maintenance. What I need to to is to auto assign a ticket to a support group with the subject of the email. for example:
Subject: "PS" -> assign to "PrimarySchool" support group

Subject: "HS" -> assign to "HighSchool" support group

Subject: "Maint" - assign to "Maintenance" support group

Can someone please help me with what I need to put in the setting for eMail Parsing?

Thanks a lot

Gary