Andre Norton used the same process in a lot of novels.
Basically, in her "future" you receive formal training in an occupational field. Those who cannot pay for a private academy (which usually is tied to a group of companies that hire all graduates) are educated by the government... but must then accept whatever assignments they are given by the government.
After you complete your schooling you are sent through a "test and evaluate" process, which includes batteries of psychological and compatibility tests.
This is to insure that all positions you are offered fit with your personality, social orientation, and mental capacities (including adaptability, inventiveness, and tolerance for tedium). Your ability to tolerate large numbers of people, or to function well in a confined ship with few crew, is also factored in.
Those that cannot fit into rigidly structured settings, but instead thrive in shifting and uncertain conditions that require improvisation and adaptability, are offered Free Trader or Scout Service openings.
Those that cannot fit into rigidly structured settings, but need a routine existence, get small Merchant Line postings.
Those that do better in rigidly structured settings, and in a routine existence, get major Merchant Line postings.
And finally, those that thrive in rigidly structured settings, and need a purposeful existence, get the chance for Navy Supply positions.