During Friedrich's glider flight, his helmet is securely strapped at the start but is shown unstrapped a few seconds later. He kept both hands on the glider's yoke.
A signage on the door, Anstaltsleiter, has wrong letter for the first "s". It should be written as "long s", resembling lowercase "f" without horizontal cross line. This practice was abandoned after the end of second World War.
At least one of the Napola boxers and one of the training officers have pierced ears. Very unlikely, this being set in Nazi Germany.
By the time Napolas were established, the phrase "Sieg durch K.o." (victory by KO) would have been avoided because KO stands for the English word knockout, the language of the enemy. A true patriot would have said something like "Sieg durch Niederschlag" (victory by knock down).