International organizations — Immunity — Jurisdictional immunity — European School in Brussels — Legal status — Dispute with parents concerning class allocation of pupil — Whether subject to jurisdiction of Belgian courts — Statute of European School, 1957, and Establishment Protocol, 1962 — Failure to provide an effective remedy against decisions of organs of European School — Whether violating Article 13 of European Convention on Human Rights and Article 2 of Protocol No. 1 to Convention — Whether Belgian administrative courts implicitly vested with jurisdiction — The law of Belgium