Final answer:
The group of students can best be described as belonging to the same cohort, sharing similar experiences with education costs and financial responsibility.
Step-by-step explanation:
The group of students mentioned in the question who started elementary school together, graduated high school during a time of high education costs, and became financially responsible due to student loans can best be described as belonging to the same cohort. A cohort is a group of people who share a statistical or demographic trait, such as being born around the same time, experiencing certain social or economic conditions, or going through similar life events like attending school during the 2008 financial crisis, which affected many young adults' futures including their employment opportunities and financial stability.