I currently fly out of New Century Air Center, between Olathe and Gardner. Several aircraft rental options at New Century Air Service with instructors available as well.
Johnson County Executive airport has a flight school - Air Associates. A little costly being a flight school but gives opportunity for the structure to get it done. I got my IFR rating with them last spring. Neither are too busy and great to work with on student training, although downtown (Wheeler) will give good practice with a busy pattern, close airspace and a nice city view.