I think that's just a combination of window grime and reflection that your mind is transforming into an image. It's called pareidolia. Couple other thoughts, however. The second photo shows the facility has been vandalized to the point of missing windows, and possibly doors. If there was someone in that window, could have been a squatter or homeless person. If you still think it could be the spirit of a maid, you might want to check with the local library or historical society to see who is the keeper of the facility archives/history. Most likely there are photos of the school's staff throughout its history, you could check to see if anyone is dressed as you perceive them to be in the photo.