naughty

defiant, disrespectful, ill-mannered, ill-natured, impolite, improper, impudent, indecorous, insolent, rude, uncouth, unmannerly

disobedient, headstrong, intractable, obstreperous, recalcitrant, refractory, transgressing, unruly, untoward, willful (or wilful)

balky, restive, uncontrollable, ungovernable, wayward, wild

elfish, impish, knavish, monkeying, monkeyish, ornery, pixieish, prankish, rascally, roguish, waggish

disorderly, rowdy

babyish, childish, immature, infantile, jejune, juvenile, kiddish, puerile