A charcoal gray A-line dress is dark enough to be appropriate but the warmth of gray makes it slightly less severe than pure black. A-line means grace in the silhouette and the shape works on everyone without requiring adjustment. Charcoal is also more forgiving in terms of showing the dirt and wear that comes from a day of sitting and standing through services. A midi length is appropriate and the structured A-line cut means the skirt moves with dignity. Long sleeves or cap sleeves feel respectful. The neckline should be simple and modest. The beauty of A-line is that the proportions are automatically balanced regardless of body type. These dresses look intentional and composed without requiring any styling risk.