In Finland you can usually complete first year of the bachelors studies without enrolling to the university. Some of the courses, like first programming courses in CS, are free. Others cost a small fee, around 75€ per course. If you decide to enroll in the uni later, those will be acknowledged as well. They also have Digital Education For All program that has all of the first year studies for free.

I personally did complete about six months worth of studies while still in the secondary education.