You'll need to measure your child's waist for girls skirts, even if the skirt style is designed to sit on their hips, it is the waist measurement that you will need.
Measure your child’s waist by finding the narrowest part of their torso; this is normally a couple of inches above their hip bone and often, but not always, in line with the bellybutton. If your child has no natural narrower part to their torso, take their waist measurement from about halfway between the bottom of their rib cage and the top of their hip bone. Pull the tape measure so it’s snug but not tight against their waist and make sure they’re not holding their breath! You don’t need to add anything to the measurement for comfort as good quality school uniform will be designed with a little bit of ‘ease’ included.
To take your child’s skirt measurement, it’s easier if they wear an existing school skirt or other skirt that they like the length of. Measure from their natural waist down to the hem of the skirt, ensuring the tape measure is in a straight line. You should also check their school’s uniform requirements for skirt length to make sure any item you buy adheres to regulations.