I checked with Poon's Transport today, represent said bus route between Shatin/Ma On Shan is yet fixed as it might be varied depending their customers (our boys) distribution after the orientation day.
I have done so, much depend on number of students taking school bus from my side Ma On Shan or Shatin to DBS. Considered there might be no direct route between two areas to DBS. It will be solved in the coming up parent's talk session.