While you are in the post of UDC, your representation and your claim is that you should be treated as Assistant Teacher. The Delhi School Tribunal has got the jurisdiction to decide the disputes relating to the teachers as well as non-teaching staff of the school. So, Delhi School Tribunal cannot oust your case on the ground of jurisdiction. But, High Court may refuse to take up your case on the ground that you have alternative remedy to approach School tribunal. Hence, my advice is to approach the School Tribunal and its orders are appealable in High Court. Regarding merit of your case, that can be decided by the Tribunal, once you file your petition.