There are a lot of discounts that are available exclusively for college students. Sometimes, however, you can work around that rule ( for example student rush tickets). We attribute it to the most common assumption that if there is a discount then college students are more likely to use a product, whereas high school students are able to get monetary assistance from their parents.
High school students don’t have loans, and housing, and textbook payments that most college students have. The majority of high school students live at their home and don’t need to pay for these things.
One does not get Spotify Premium until he convinces the rest of his family to share the family plan. It would also be cheaper to do that, even if he could get a student discount.