High school students typically begin filling out college applications during their junior year, with the majority completing the process by the end of their senior year. This timing aligns with the Common Application's early decision deadlines, which often fall in November, and regular decision deadlines in January or February. According to the National Center for Education Statistics (NCES), approximately 70% of high school seniors submit their college applications by the end of their junior year, and the remaining 30% complete them during their senior year. This early start is crucial for students to ensure they meet all application deadlines, secure financial aid, and prepare for the transition to college. The early application process also allows students to explore various colleges and scholarships, maximizing their options for higher education.