Technically it's working as it should, since the string "Insert Facility Here IT" contains the string "ER" (in the word here). Maybe changing the case statements to something like the below (just added ='s to the beginning) will do the trick...Since it will not evaluate true if a portion happens to appear in the middle.

 Code:
select

	case instr ($OU,"=Business Office") and instr ($OU,"=Computers") and instr ($OU,"=Insert Facility Here")
		? "Business Office"
	case instr ($OU,"=Education") and instr ($OU,"=Computers") and instr ($OU,"=Insert Facility Here")
		? "Education"
	case instr ($OU,"=ER") and instr ($OU,"=Computers") and instr ($OU,"=Insert Facility Here")
		? "ER"
	case instr ($OU,"=Training Room") and instr ($OU,"=Computers") and instr ($OU,"=Insert Facility Here")
		? "Training Room"
	case instr ($OU,"=Specility Clinic") and instr ($OU,"=Computers") and instr ($OU,"=Insert Facility Here")
		? "Spec Clinic"
	case instr ($OU,"=Insert Facility Here IT") and instr ($OU,"=Computers")
		? "IT Printers"
		;printer_map("$printserver",'IT-PR2')
		;printer_map("$printserver",'IT-PR3')
		
endselect