Good reasoning, Valvegear. It may well have been near their homes. But I would speculate that neither their homes nor the school were near Carlsruhe, as it isn't the answer.
I'll give you a bit more of a clue: The story goes that the closure was posted in the relevant Weekly Notice, and very shortly afterwards, it came to the notice of the powers that be that these two girls had purchased yearly tickets. So an amending Notice appeared, stating that I was closed to all traffic apart from one specified down train and one specified up train; and these trains would stop only if required, "and only for Misses [Schoolgirl 1
] and [Schoolgirl 2
]". As soon as the tickets expired, the bulldozers moved in.
Of course this may be all an urban railway myth, but that is the story as recounted to your informant. I'll understand if you feel sceptical. If the answer is not provided by tomorrow, I shall give a clue of a more conventional nature.