The idea that a single recommendation at twelve sets a child's academic ceiling alarms parents arriving from systems that stream later, or not at all. Dutch secondary education really does sort pupils at that age, but how the advice is formed and which routes stay open afterwards is rarely explained to newcomers.
There's real streaming at that age, but it's less rigid and less final than it sounds from the outside. At the end of groep 8 (the final year of primary school, around age 12), your child's teacher writes a schooladvies — a recommendation for vmbo, havo, or vwo — informed by a mandatory end-of-primary eindtoets, and since a 2014/2015 reform, that teacher advice is what actually leads; the test can only push the recommendation upward if the score comes in higher than expected, never downward. From there, plenty of routes stay open: many schools use a brugklas that combines two levels for the first year or two before the final split, so the age-12 decision often isn't locked in until 13 or 14 anyway. Stapelen — finishing one level and continuing straight into a higher one, like moving from vmbo-t into havo 4, or havo into vwo 5 — is a normal, well-worn path, not an exception. Some schools also run dakpanklassen spanning two adjacent levels specifically to delay the split further. So yes, age 12 matters more here than in some other systems, but treat it as an early placement with several built-in on-ramps upward, not a single test-locked verdict on your child's entire trajectory.