This statistic presents the average age of freshmans for the most selective universities in the US. While the average entry age for top 20 universities is 20.9 years, average age of freshmen in Dallas Nursing Institute (DNI) is 32. But its also worth noting that in 2017, DNI's student population was only around 300. High average age of entry for other institutions like Harvard University and Columbia University is attributable to their large grad student base. For instance, 8,500 students were in undergraduate programs and 21,000 in postgraduate programs at Columbia University last year.