Carter did not avoid service. He was a student at the USNA. He was not commissioned a naval officer until after the war. He served just over seven years on active duty.
I said he avoided WWII, not that he avoided peace time military service.
Jimmy Carter graduated high school in June of 1941, by the time he switched from Georgia Southwestern and then to Georgia Tech, and then finally to the Naval Academy in 1943, he was assured to never having to participate in the war.