Saved By The Bell At Thuringia High School
I found the perfect template for Imperial Germany and just couldn't resist. Here's another chapter in my neverending story about a surviving Weimar Republic after the Stresemann and Schumacher presidencies. This map is supposed to play in the early 1970s. Yes, I know that Anhalt is still there, but I didn't care.
School reform has always been a culture war between leftists and rightists and IOTL, the rightists essentially won the culture war against the comprehensive school by varying degrees of success and the rollback also hit the former GDR that used to have an excellent comprehensive school system. Besides a parental desire to hopefully keep their children from playing with mucky pups and the stronger federalism in the FRG compared to Weimar, I see another reason for the OTL survival of two-/three-tire secondary schooling in Germany in contrast to their deaths in Britain and France: Germany lost many of its old Reich institutions and symbolics after the war and the Gymnasium was one of the last legacies of the good old times.
Politically, Thuringia used to be very polarized in the 1920s and 1930s. There was an SPD-KPD coalition government that fell to an imperial execution in late 1923 (and that already planned comprehensive secondary schooling, not just the 4-year primary school in Reich-wide introduction). Just as IOTL, Thuringia got a short-lived Nazi state government in 1930, but due to the alternate Reich developments, the Nazis quickly died and the extreme right lost a lot of its credibility. The extreme left however wasn't quite as dead and this moved Thuringia left enough to give the Comp their final try in the 1950s. They created a school system that's comparable to the OTL Danish system: 9 years of comprehensive school, 3 years of lyceum/sixth form/you name it and a preparation year inbetween. Unlike OTL Denmark, where it's not compulsory but overwhelmingly attended, TTL's Thuringia tests you if you have to take that year or not.
Other states have found other ways to cater students with a second chance without sacrificing their sacred Gymnasium cow. Under extra-ordinary circumstances, students that made their way to the GCSE via Volksschule/Hauptschule or Mittelschule/Realschule and got acceptable grades therein may take the final lyceum classes of a regular Gymnasium. But usually, those unjustly treated souls will do at a vocational sixth-form (they also exist in Thuringia as a variety of the lyceums) that will have a specialized profile with some special subjects and you can actually make fully legitimate A-levels (or Abitur as we say in Germany or Matura elsewhere) there and make up for lost time without losing time.
This may all sound alright if there were enough places for all these lateral entrants of various kinds if there were enough places for everybody, but there aren't. As IOTL, Bavaria has a relatively strict policy in this regard and the supply for said sixth-form schools leaves a lot to be desired, especially in rural areas. Saxony as a stronghold of the SPD is still struggling the make the desired comprehensive school a reality, but it's ready to offer second chances more light-heartedly. Prussia is somewhere in the middle, the East Elbians have finally become managable, but it's definitely struggling between a great tradition and an ambiguous future.
Urban legend says that the later expansion of Thuringia and the dissolution even of Prussia "proper" was also due to teeange numerus clausus refugees that voted with their feet. In the end, it's just a short train ride to cross the border. The lot of student from Erfurt taking the train to the west or east partially made for a drain from their local school while school boards in places like Gotha and Weimar or even in adjacent suburbs of Erfurt that belonged to "Little" Thuringia instead of Prussia were unhappy that Erfurt didn't pay its share for the schools that part of its kids were attending. On the other hand, Erfurt as a city also provided services to Little Thuringian that they didn't directly pay for and in the end, Thuringian principles were proud of their schools. By the end of the 1970s, Prussia has ceded its Erfurt province to Thuringia, but while this may be seen as one of many instances leading to the later final dissolution of Prussia, it shall be noted that Berlin and Weimar jointly oversaw the preemptive conversion of the local school system to match that of Little Thuringia when it finally came home.
As mentioned on the map, Thuringia isn't the only destination of high school tourism. Many Franconians go to Thuringia for sure, but some from Hof an der Saale go to Saxony which may not be the El Dorado like Thuringia, but still has lower entry requirement than their Bavarian home schools. Some better-performing student may actually the reverse route, from Thuringia to Saxony, though less to Bavaria. Prussian-Saxon border traffic also occures on a noticable scale. The biggest relative exporter of sixth-form students is Erfurt lying conveniently in the middle of the Thuringian city chain, the biggest relativ importer so to speak is the city of Altenburg, lying conveniently between Leipzig on one side southwestern Saxony on the other. But due to the special political geography of "Little Thuringia", the small state was essentially bleeding students inside out.