I’m from Germany and was a sprinter during my high school years in Schleswig-Holstein, adjacent to Lower Saxony.
Mike is right, it’s the local clubs that do all the youth work. Coaches are required to get a licence to train athletes, the licence program is pretty decent as far as I know and takes about 3-4 weekends with an exam at the end, and it has a focus on the development of younger athletes, i.e. not doing too much to soon, suitable games etc. If someone is good enough and catches the attention of the state coach, there is a program with weekend clinics and a small stipend for equipment.
High school programs are almost non-existant. There’s one team competition with three meets per year (county -> state -> national), where the winner of one qualifies for the next. The Nationals are traditionally held in the Olympic stadium in Berlin, which is always a lot of fun. I made it four times in a row with my team, placing third twice, only bested by East German sports schools. It was basically a weeklong field trip with one day of competition. Good times.
College programs and regular competitions do not exist. There’s one national university championship, which is a meet like everyone else, except that you have to be a student to participate.
So it’s really the small clubs. But these are really abundant in Germany, every town and village has one.
Lower Saxony has some decent clubs, Hannover and Braunschweig most notably.
Participant