Complex sentence: Wanting to express his patriotism, he wore his ROTC uniform to school and in public, and when he turned fifteen, he dropped out of high school to join the Army by lying about his age.
Split into simpler sentences: Wanting to express his patriotism, he wore his ROTC uniform to school and in public. Not long after turning 15, he dropped out of high school and joined the Army by lying about his age.