When I was studying Chinese in Changchun in 1990, I lived in a dorm room that faced the sports field. Every day for the first month of school, the freshmen would spend the day marching around the field. Sometimes they would practice shooting (fake) guns; sometimes they would practice martial arts moves; but always they would march. “YI, ER, SAN, SI,” (1, 2, 3, 4) they would yell as they marched.
Whatever were they doing?
This short video gives a good overview of what was (and still is) really going on.
One thing those kids learned for sure — they could count to 4 in unison like nobody’s business!