My son got this. He arrived in Switzerland aged 10, with no German. He got to secondary, having got the highest maths results in the canton, including a question no-one else solved. He went to Gym, and ended up with a masters in Physics from Basel University. Throughout that (University excepted), the refrain from a few teachers* "Your German is not good enough..."
My daughter rose from Real Schule to Secondär to Gym. Thence to a prestigious apprenticeship, BM, now studying for a degree in Pharmaceutical Engineering at the FHNW. Throughout that (FHNW excepted), the refrain from a few teachers* "Your German is not good enough..."
My other daughter, Secondär, FMS, (Got a degree at the Open University in French and German), C2 German from the Goethe institute, and now at an FH to gain a teaching qualification for Primary. throughout that (OU and Goethe Institute excepted), the refrain from a few teachers* "Your German is not good enough..."
In all cases, their German teachers have said "What? Your German is fine". Weird, huh? I wonder who is right?

(The sad thing is, some of these people make decisions based on their unqualified opinion)
(Flameproof jacket donned. Go for it).