Co-ed bathrooms at work?

So, I'm working at an all girl's school this year and the staff bathroom is co-ed. This is a little strange for me... especially coming out of the stall, and seeing a male teacher heading to the sink at the same time as you. There is just a micro-second when I think "What the heck is he doing here" but then I remain cool and say hello and we proceed to wash our hands and exit.