Pretend you are a teenager
Now pretend that your parents (the governor & first lady of your state) send you to boarding school in the SAME TOWN YOU LIVE IN.....
How could that NOT affect your perception of your own self-worth?
How could you NOT wonder why you had to live at school while your own bedroom & the freedom of family life at home was but blocks away?
Unhappy, rebellious teens often lash out.
I am from the same era as Mittens. and I knew kids who went to boarding school. We even HAD a boarding school in our town ; St John's Military Academy. These boys were usually from wealthy families who did not want to "bother" with them, but EVERY single one of them came from somewhere else.
Boys who were a "handful", and whose parents could afford it were the ones who got sent to these schools to "straighten them out".
The the girls I knew who did go to boarding school, were sent because of a divorce in the family (nasty work back then), or a special skill (music, etc), or to study abroad (one went to France for a year)..
A biography of George Romney said that he & his wife were called "the Bickersons", because they argued so much, so maybe Mitten's home-life was not as rosy as he pretends.