This never seemed to me like a possibility, and I don’t think the kids worried about it too much either. Even when I first went to uni in the 90s, many of my fellow students were not school-leavers and had entered uni via an alternate route. I've just enrolled myself in another university course, 25 years on, and the process was quite simple and 100% online.
When my older kids were teens, a Certificate course was a good entry path into further education, so they started studying those as part of what would be their “senior studies” at around 15. For the younger kids, they also chose certificate courses, and they are also accessing bridging courses into their preferred field. These courses are offered by many universities, and I wish that’s how I entered uni – instead of leaping from high school into the foreign land of tertiary study!
Five of the bigger kids have completed Certificate Courses (such as a Cert 3 in Business, or a Cert 4 in Fitness, for examples), one did a Diploma course, one did a bridging course and one is planning to enrol into a bridging course before their degree. One also did an apprenticeship in an unrelated field, did a Bachelor degree and is now doing post grad study as well. None of them had any issues with entrance into these courses. I feel as though we’re at a time where high school scores are less relevant than ever.