It's not true. At least for Germany. Take a friend of mine for example: He went to Hauptschule (Germany has a 3-tier school system where children are split up after primary school, Hauptschule is for the least skilled children). He left Hauptschule a year early with very bad grades to start an apprenticeship with a carpenter. After three years of school and practival training he graduated to journeyman with honors (i.e. all grades: A). This gives you a scholarship for master school or college (if you want). He chose master school and earned the master craftsman degree. He finished that with honors, too and got another scholarship. Now he actually went to university to get a bachelor in something called wood-technology.
In many academic traits it's actually beneficial to go for an apprenticeship first. Architects often become carpenters of masons before studying architecture, a friend of mine who's a nurse got her Dr. med. last week. The list could go on for a while.
But thats one track. Say you went carpenter route when you were 15 and now you want to study medicine or electronics or CS. You are going to lack basic background: even with master school it is really going to be tough to learn all the chemistry, mathematics, biology or physics that is required for those majors.
The system is build as a training for just one type of work and nothing more. (if we are not talking about gymnasiums) So changing tracks means starting from zero again. It is doable, but very few people want to start again in class full of 15 years old, second problem is money: there is nothing like student loans. Also society will view as a failure.
