My son came home from school w…

My son came home from school with a note from his teacher yesterday. It said that he had detention for a week because of “poor conduct in a mathematics class”.
The teacher asked him “if I had 5 chocolate bars then bought 5 more, how many would I have?”
Apparently whilst the answer “10 too many you fat bitch” is mathematically correct the “tone” of the solution was “offensive”.