The problem is that (in Germany) many students/pupils cannot even read properly. There are many who are simply not able to read a normal German text, even if they are already in the fifth grade.
And then on the one hand we have here in many schools the broken concept of the so called integrated comprehensive school. And they have to find the lowest common denominator to get everyone, even the most incompetent, through school somehow. And because the schools all want to proclaim success, they simply lower the required level.
On the other hand, more than 3 out of 10 students are no longer native German speakers, which makes the level even worse. According to my older sister (a high school teacher), in some schools there are classes with only one or no native German speaker anymore.
Not politics, but statistics.
Internationaler Vergleich: Fast ein Viertel der Schüler in Deutschland erreicht die Mindeststandards nicht. (International comparison: Almost a quarter of students (i.e. pupils) in Germany do not meet the minimum standards):