They're four years apart in age, so best case is her having been in third year of middle school and it was close to the end of the year, making her 15, and him 11. Worst case she was in first year and at the start of the year, so she'd have been 11 and him 7. She's got on the winter uniform top (long sleeves), so it could go either way really. No matter what he was definitely in elementary school still.