"Betragen ungenügend!" is the seventh and final film from the West German German-language film series about the Lümmel, a bunch of students who keep playing pranks on their teachers, led by Pepe Notnagel (Hansi Kraus). While Kraus was the star early on in the series, the focus switched more and more away from him to veteran actor Theo Lingen who played the school's principal in all these movies. And in this last work, it is all about him being forced to retire or retire voluntarily and spend more time with his family. But when it's about to happen, the students realize that they actually love their principal. This 85minute film is my second least favorite from the franchise and only the sixth film is worse. Luckily, here the action is once again at the school for the most part and it is also a bit about the pranks again. However, I did not like at all that Knörz was depicted as a main antagonist here and suddenly power-hungry and mean. I always saw a likable slob in him in the previous films. It's fine they wanted to go for some character development, but in my opinion it was not working out. So the franchise ends sadly on a low note after being really prolific with 7 films in under 5 years. Kraus had clearly grown up by the early 1970s. The thing I liked the most here was probably the music and the ending was actually kinda touching too. But 2 strong songs and Lingen's convincing way to close the franchise are not enough to make up for all the mediocrity. I do not recommend the watch. Thumbs down.