No, you did not say that you were knowledgeable, but you did imply that you were of a higher knowledge base in this area than he, based on the classroom time...
try using some different words instead of derivations of derisive too...
abusive, arrogant, audacious, aweless, back-biting, bantering, belittling, biggety, bitchy, blackening, blameful, bluff, bold, booing, brash, brassy, brazen, bumptious, calumniatory, calumnious, catcalling, catty, censorious, chaffing, challenging, cheeky, chutzpadik, cocky, condemnatory, contemptuous, contumelious, crusty, damnatory, daring, defamatory, defiant, defying, denunciatory, deprecative, deprecatory, depreciative, depreciatory, derisory, derogative, derogatory, detractory, discourteous, disdainful, disparaging, disregardful, disrespectful, execrating, execrative, execratory, facy, fleering, flip, flippant, fooling, fresh, gally, gratuitous, greatly daring, grinning, hissing, hooting, impertinent, impudent, insolent, invective, inveighing, irreverent, jeering, joshing, judgmental, kidding, leering, libelous, malapert, minimizing, mocking, nervy, objurgatory, panning, pejorative, pert, priggish, quizzical, ragging, railing, rallying, razzing, regardless of consequences, reproachful, reprobative, reviling, ridiculing, roasting, rude, sassy, saucy, scandalous, scoffing, scurrile, scurrilous, slanderous, slighting, smart, smart-alecky, smart-ass, smirking, sneering, snickering, sniggering, snorting, taunting, teasing, twitting, uncalled-for, vilifying, vituperative, wise-ass