We distribute printers through GPO and OU Units

we have on printer per OU Unit set to per machine

ie F24 machines 1-15 get printer 1 in that room
F24 machines 1-30 get Printer 2 in that room
F26 machines 1-15 get printer 1 in that room etc

everything works ok and the printer is deployed

but for some reason everyone that logs on is getting every printer from every room throughout the school

any ideas