You are Right.But Some of the District authority (D.P.S.C), authorized to concern Sub-Inspector of Schools as a leave sanctioning authority In case of commuted Leave, Medical Leave etc. As for example Bankura D.P.S.C. one of them.
In case of Casual Leave:- Head Teacher’s application be made with the recommendation of Chairman, V.E.C to S.I/S.
All A.T’s through H.T. to S.I/S.who is the sanctioning authority accordingly.