The obstreperous behavior of the students inside the classroom drew the attention of the Principal.

Obstreperous means noisy and difficult to control, unruly, or disorderly. The word disorderly directly captures this meaning of being unruly and out of control. Compliant means the opposite—willing to obey rules. Obnoxious means extremely unpleasant but doesn't capture the noisy/unruly aspect. Inconspicuous means not easily noticed, which is the opposite. Therefore, disorderly is the best synonym.