Enrollment in US high schools has ranged between 2.5 million and 4.5 million across grades 9 to 12 from 2000 to 2024. However, projections indicate a change in enrollment patterns by 2031, with enrollments in grades 11 and 12 projected to fall below 3.5 million, while grades 9 and 10 are expected to remain around 3.8 million.  This projected distribution implies a potential drop in student progression through high school over time. The potential decline in upper grades can be attributed to changes in grade promotion (advancing to the next grade), transfer rates, and dropout rates which have influenced students' progression through high school. Pandemic disruptions, declining birth rates, and the availability of state choice programs offering public funds for private school tuition have further contributed to the longer-term decline in high school enrollments.