When I was in 10th grade I took a year of french because it was required. The teacher was known to go off on tangents sometimes and one day she told the class a quick story about how during WW2 when the Nazi's invaded Paris, that there was this large battle that took place between the Paris police force and the Nazi invaders at the police HQ. I did some googling earlier today after randomly remembering this story, but wasn't able to find much information backing this up. Did something like this ever happen during the invasion or was my french teacher mistaken?
I suspect that either you or your teacher has mixed up the invasion in 1940 with the liberation in 1944. In 1940 Paris was declared an open city, and there was no resistance when the Germans entered it. In 1944 the Resistance rose in rebellion a few days before the 2nd Armoured arrived; the police came out in support of the Resistance, and the police HQ was the first public building to be taken over.