Dan has answered your question very well. I'd just like to add the following information:
In the US, a college (university) education usually takes four years to complete. The first-year students are called "freshmen" (singular: "freshman"), the second-year students are called "sophomores," the third-year students are called "juniors," and the fourth-year students are called "seniors."
American high schools also usually offer a four-year program -- grades 9 to 12, and the same terms "freshmen" etc. are also used for the high school students.