The decision was described on Wednesday as a “catastrophe” by the head teacher of the school in Neuwied in Rhineland Palatinate, while the girl's parents said they were “totally devastated” – and furious there was no chance to take the case further.
Generally people over 21 can have sex with 14-year-olds unless they abuse the younger partner's "lack of capacity for sexual self-determination" or are in position of power over them.
The district court in Koblenz overruled a 2010 conviction of sexual abuse of a ward – and lifted the accompanying two-year suspended sentenced handed down by other, lower courts, because the judges decided the man was not her teacher.
The 32-year-old man had only taught the girl's class a few times as a substitute teacher, which the court decided was not enough to classify her as his ward.
Speaking to the Rhein Zeitung newspaper, the girl's father said it was an admission of complete failure to say that a substitute teacher had no duty of care.
The married teacher, whose subjects included religion, maths and English, faced the loss of his teaching license as well as his civil servant status and the benefits coming with that status.
He appealed, and was told by the next judge to deal with the case that he should be happy with the initial sentence – that he could have come out much worse.
But he continued to fight the sentence and it has now emerged that the Koblenz judge agreed with him, absolving him in December.
Der Spiegel reported that the girl and the teacher had first become chatty during a bus trip to Hamburg back in 2006, sitting together and talking for several hours.
They then communicated via an internet chat service, and he had at one point asked her to send him intimate photos.
By January 2007 the first sexual contact occurred and they met regularly for sex over a period of nearly five months. She is said to still be in therapy, five years on.