A Bronx mom unhappy with how her son’s high school disciplined him lashed out at the new principal yesterday — bonking him on his head, scratching his lip and paying for it with a ride to the clink, authorities said.

Alba Ramirez, 41, was charged with second-degree assault stemming from the morning mash-up that scuffed Art & Design HS Principal Eric Strauss, police said.

Teachers at the Manhattan school said the squabble arose after Ramirez demanded a meeting with the principal because she thought a dean had inappropriately scolded her son and spoken disrespectfully to her.