How will the child build a career without going through college?

Simply put there is no one way, rather many organic ways. First the child develops basic skills in his or her field using loads of self work, coaching, projects, courses and workshops. Most children, once ready in terms of their skills and age, hop onto internships, apprenticeships, mentorship or even taking jobs. Rest is learning on-the-job, obviously again boosted via self learning and courses and workshops. The child constantly takes support from industry experts as well as is guided and supported by family and community. Notably the child builds his own set of peers either in the same field or just a group of supportive friends who give the child the necessary social group.
All throughout the journey the child builds a portfolio to show in case required for any job interview or to bag freelancing projects or even financial support.