There is two teachers. H.T. (joining date 1988) and other A.T. (joining date 2012.) Another A.T. is transferred in this School in 2013 whose joining date of service is 2010. Now in this school, is he 2nd teacher or 3rd?
I think you are talking about primary school. In that case the teacher whose joining date (in the service, not in school) is earlier will be considered as senior. So, the teacher who has been transferred will be considered as service senior.