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.
I dislike Jimmy Carter as much as you, but this is BS. No one in 1943 knew how long the war would last. They were planning the invasion of Honshu (Operation Coronet) for 1946. So it was highly likely Carter would be in it as he graduated in 1946.
Look at that timeline, he was scheduled to graduate in 1947, 1941 to 1947, three different colleges, he was doing the best he could for a fit young man.
Reagan on the other hand already had about 5 years as a Reserve Cavalry officer when he was called to active duty and then tried to finagle a combat position in spite of his eye problems.