Purity Balls - events where fathers vow "to protect their daughters in their choices for purity" - are now a full-fledged national phenomenon occurring in 48 states and in as many as 17 countries.

In October, our team was invited to attend the Super Bowl of Purity Balls at the regal Broadmoor Hotel in Colorado Springs, Colo.

It was the 14 th annual Father-Daughter Purity Ball, and 60 fathers signed a purity covenant , promising, "before God to cover my daughter as her authority and protection in the area of purity."

Watch an encore presentation on "Nightline," Tuesday, March 25 at 12:35 a.m. ET.

Girls rehearse for the ballet performance they will perform at a purity ball. Credit: Victoria Thompson/ABC

From left to right, Kameryn Wilson, mother Lisa Wilson, Kaalyn Wilson and Jordyn Wilson. Credit: Victoria Thompson/ABC

I first contacted Randy Wilson-the founder of the first of these balls-over the summer. He invited us to spend a few days with his wife Lisa and his seven children. They were an exceptionally warm group, greeting us with homemade cookies and glitter-strewn cards.

The Wilson kids were all home-schooled and the purity lifestyle was evident everywhere, from the blessings Randy conducted with them in their backyard to the purity rings all the kids over the age of 12 proudly wore. Some of the older Wilson children were already married and had all experienced their first kisses at the altar on their wedding days.

In such a tight-knit community of other like-minded young people, they claimed to be at ease with their choices, their views seemingly unchallenged in their daily routines. We tagged along for ballet rehearsal with 17-year-old Kameryn, and hung around the house while the girls all did each others' hair in preparation for the big ball. I had never met a group of siblings (at least with the cameras around!) who were so nice to each other at seemingly every moment.

Through the Wilsons, we met a second family, the Johnsons from Indiana. Like the Wilsons, this was an exceptionally welcoming, sweet family with seemingly no harsh words shared between them. Unlike the Wilsons who were homeschooled, the Johnson girls went to school with other kids, many of whom did not subscribe to the purity lifestyle. They played on sports teams and planned to attend school dances (with platonic dates, of course).

The Johnson family seen here gathered around the table as "Nightline" producer Victoria Thompson films. Credit: Victoria Thompson/ABC

"Nightline's" Cynthia McFadden interviews Katie Johnson, 17. Credit: Victoria Thompson/ABC

We hung out with them at home as they had big family dinners, tagged along for milkshakes with 17-year-old Katie and her soccer team, headed to the school cafeteria with 12-year-old Caroline and attended a basketball game where 10-year-old Alicia was cheerleading.

These were typical American kids doing typical American activities. However, they were part of a close church community led by their dad Ron, the head pastor at the Living Stones Church. Older sister Katie admitted she probably couldn't have adhered to this lifestyle were it not for the extremely tight bond with her church friends, without whom she would probably "give up."

It was a fascinating look into this world.