The system you refer to is and in many regions had been phased out as it turns out that the splitting around 6th grade isn't really working well.

Also even before you had schools which covered multiple of this schools and allow students to "move" between them, sometimes in a per-course level.

There also always had been ways to get the same degree as from a gymnasium even if you initially ended up on a hauptshule, through it was a often shitty path and potentially took you a bit longer. While a few people which state out in a realschole doing it was the norm, for people on a hauptschule it was very very very unlikely.

Don't get me wrong the German school system is a mess, especially if composed to some of the Nordic states but it still beats the US.