Complex sentence: It usually includes a very short (sometimes short enough to reveal the underwear, or lack thereof), pleated skirt such as real schoolgirls wear for netball; in any case, the skirt (trousers are rare in such outfits) rarely goes below the knee.
Split into simpler sentences: It usually includes a pleated skirt such as real schoolgirls wear for netball. It can be very short (sometimes short enough to reveal the underwear, or lack thereof); in any case, the skirt (trousers are rare in such outfits) rarely goes below the knee.