Caste and class systems do cause inter-class resentment, but history has shown that it is usually not enough to tear a society apart. Such resentment can even be useful to make the working class recognize that it has to stick together to get a piece of the pie (cf. social democracy). So now you have decent conditions for the working class and it's somewhat respected by everyone. Being working class is not a stigma, it is... just less prestigious.
The German school system creates a kind of stratified society - do note that it selects nominally by actual ability (in fact the parents are quite important, independent of other factors). A small problem is that the lowest stratum has become the lowest few percent and, like almost everywhere, education standards are decreasing in the now enlarged highest stratum. Electricians (my parents know one) are struggling to find good enough apprentices, and some academics have trouble finding work because there is no demand for their academic skills.
Do note that evening schools to prepare blue-collar workers for university exist.
It is all very un-American and counterintuitive, but stratified societies seem to work. Of course I recognize the downsides - inequality of chances and lost opportunities. Very likely my opinion is also rose-colored because I grew up in and benefited from a time of great upwards mobility.
AFAIU, the class system in the UK is stronger and less permeable than the German system. The French system seems more permeable but it has a special kink in that it is stratified at the highest level - you either get into one of the top three or so Paris universities or you don't. More than half of all French industry leaders come from these top universities.
This isn’t true. Germany is the second most credentialist, title obsessed country in the world, with a class structure as obvious as in the UK, if different.
I don't even remember what they choose in the end. I think just a dropdown box. I probably told them I'm make the list of titles to choose from configurable in their backend system and they could make it however they wanted later - which nobody probably ever bothered to do.
Otherwise you basically have no other options than to do an apprenticeship or a trade school after middle school.
Which is much better than doing nothing at all, or going for some useless degree in college that will take you to debt.
Not everyone is smart, I am one of those people (pretty dumb), it is fine.
Do that in the US, and we'll just end up with blue collar wage slaves instead of white collar ones.