Do ordinary citizens of Academy City know about the existence of magic? By ordinary citizens, I mean the general population of the city.
You can read the Wikia article on Academy City:
In the novel series, there are only a handful of residents who know about magic, either due to encountering it or being part of the magic side themselves, such as Kamijou Touma, Index, Accelerator, Hamazura Shiage, Aleister Crowley, Heaven Canceller, Tsuchimikado Motoharu, Himegami Aisa, Etzali, Xochitl, Misaka Mikoto, Kazakiri Hyouka, Othinus, Tsukuyomi Komoe, and Kihara Noukan.
It further states:
Although Academy City is stated as the dominant faction on the Science side, there are still internal conflicts with the science side, not unlike what's happening in the magic side between the various churches. Because of their stance as the most advanced city in the world and having the capability of producing supernatural powers, they are both envied and feared by the factions on both sides. Even then before the start of the series, Academy City has remained neutral towards Magic side affairs in the city, allowing magicians to enter the city and not intervene with their business even at the cost of lives, and having other magicians deal with magicians without reporting to the magicians if there are third parties involved. As magic still remains hidden to the world thus, much like Oyafune Monaka, almost all of Academy City's residence are oblivious of such areas and would consider them to be another form of esper powers. Only a few, such as Kihara Noukan and Heaven Canceller, are aware of the existence of the magic side.