What option are available to you? Is it a uniform (only one way it can look) or a dress code (could be straight or pleated, or choice of a few school colors)? If it is a uniform, can you alter the length of the skirt? If a dress code, do you have options for perhaps different colorways? My kid’s school allows a few different options even within the uniform (pinafore vs skirt & blouse, for example). My experience is that narrow kids tend to be narrow more similarly, while broader kids are broad in all different shapes. Could you try on a few options in her regular clothes that are similar in cut to her uniform to help get a sense of what most flatters her specific shape? I know uniforms can be so expensive. It might be a cost-saving way of figuring out which direction to go.