1. Sure some of the girls probably attended athletic events, but Kavanaugh wasn't in the stands interacting with the girls. He was on the court or on the field with his all-male team. Any interaction would have been reserved for the parties held after the games, parties that included alcohol.
2. Some of the girls probably attended the same church as Kavanaugh, but a church service doesn't offer much opportunity for interaction between the sexes. His ability to participate in church youth groups would have been limited. Remember, Kavanaugh was one of the top students in his class. He spent all day in an all-male school, followed by a couple hours of athletic practice, followed by considerable time hitting the books to maintain his status in the class. That leaves weekends and summers for socialization, which coincides with his schedule of drinking with the boys and a few girls.
3. With very few Monday-Friday opportunities for normal socialization with the opposite sex, Kavanaugh was pretty much limited to weekends and summers. Hanging out with girls on weekends and during the summer usually involved plenty of drinking, and Kavanaugh's behavior was impacted by his drinking. Have any high school girl friends (not friends who happen to be girls, but one-to-one girl friends) stepped forward to describe his gentlemanly behavior? Not that I'm aware of. His interaction seems to have been limited to group activities, once again with heavy drinking playing a large part. Did he have a steady girl friend that can vouch for his behavior when the two of them were alone? No such girl friend has been brought forward to defend him.