Dear Tanima,
Why Casual leave in medical ground ? In case of medical leave, a question arise medical Certificate or Fit Certificate etc. But, No problems in case of Casual leave. Sanctioning authority in case of C.L. is H.M. In case of M.L. it is M.C.( In case of Primary School , S.I/S & D.P.S.C. respectively). Is not it Tanima? Take care.