Spot the odd girl out

Two trios of schoolgirls. All attend Monivae College, Hamilton. In each trio there is an odd one out. Can you spot her?

Monivae College - girls trio in summer dresses with an odd girl out (mary janes)

Monivae College - girls trio in summer dresses with an odd girl out (elastic strap ballet flats)

Did you check their shoes? All are wearing t-bars, except for the one girl in mary janes, and another girl in elastic strap ballet flats.