It took Paul Berry a while to figure out why the fifth-grade students in his physical education class kept asking if he liked coffee yogurt.

Eventually, the budding matchmakers at National Cathedral School came out with it — giggling as they mentioned their pretty English teacher. Coffee yogurt is Ryann Williams’s favorite.

Berry had met Williams a few times and would say hello at faculty meetings, but he assumed she was married. When she appeared in the campus training center for a fitness assessment in June 2008, however, he noticed she wasn’t wearing a ring. He also noticed that her birth date made her five years older than him.

Williams said she wanted to train for a 10-mile race but didn’t really know where to start. Berry offered to meet up for a run. “Most of the time I say these things and people are like, ‘Um, okay, I’ll call you.’ She said, ‘What time?’ ” he recalls.

They set out on a Saturday morning, chatting along the way about her childhood in the District and his in Hagerstown.

Williams’s father, who was also a P.E. teacher, died when she was 9, but she and Berry both grew up in households that were strong on faith and family. “I just felt very comfortable from the beginning,” she says.

But she was flustered when he suggested they have dinner sometime. Berry didn’t necessarily intend it to be a date — he’d always vowed not to go out with an older woman because “she’ll have a plan before you even meet her” — but he enjoyed Williams’s company and thought they’d have fun hanging out.

Williams was hesitant, fearful they’d be crossing a line. “I was very conscious of work,” she says. “It was very important to me to be professional and respectful. I feel like I set an example for the girls in my behavior.”

A friend’s nudging persuaded her to agree to dinner. At Zengo in Chinatown, neither was sure the meeting was romantic. But after several hours of nonstop chatting, they noticed they were the only customers left in the restaurant.

“Ryann is very proper, very polished. I thought I knew what I was getting into when I started talking to her. I thought I had her figured out. But I didn’t,” says Berry, now 28. “She laughed. And her laugh caught me by surprise — it was deeper, a little sultry. I said, ‘There’s something to this.’ ” And with that, his rule about older women went out the window.

A few days later they met up to play pool. At the end of the evening, he walked her to her car, where they sat talking until the sun came up. Before he left, he kissed her. “We just wanted to prolong it and spend more time with each other,” Berry says.

Soon they were hanging out several nights a week, trying new restaurants, going to concerts and exploring the city. For years, Williams had prayed that her father would help her find a man who loved her the way he had loved her mother.

And after we had these conversations and were getting to know each other, I looked at him and thought, ‘There’s something about him that just feels like a little piece of my dad that’s with me,” she remembers. “I just felt this huge peace and comfort. And there are so many similarities between him and my dad, too.”

Besides being P.E. teachers, both men possessed a strong commitment to serving others. And both were the quiet types who spoke when they had something important to say.

Still, Williams remained anxious about the situation at work. They generally avoided each other on campus, although a new batch of fifth-graders took up where the last class left off, trying to get them together. “I had to really keep a straight face,” Berry says. “Because I was like, ‘Do they know? Can they sense something?’ ”

Life got a little easier after a year, when Berry left to pursue a graduate degree in exercise science at George Washington University. And in the fall of 2010, Williams completed her 10-mile race — with Berry running beside her. “Everything I’ve wanted to do, he always makes me feel like I can do it,” she says.

The next month, when she was in her pajamas grading papers, Berry showed up with flowers and an engagement ring. “Ryann is the person you want to have to make the world go ’round,” he says. “And she makes my life go ’round as far as the way she inspires me every day.”

The next day, there was the little matter of explaining the diamond to her colleagues and students, who had no idea she even had a boyfriend. “But to who?” she remembers her lower school director asking after she announced the engagement. As word got out that it was Paul Berry, she started hearing from colleagues and NCS parents who wanted to rave about her fiance. “I would get these e-mails from parents with stories of how Paul treated them with such kindness, what a great person he was. It just reminded me, even more so, why I love Paul,” says Williams, now 33.

On Oct 14, the two were married at the Church of the Annunciation. Berry’s father, a pastor, stood up as his best man. At the Fairmont Hotel, Williams’s mother kicked off the reception with a tearful speech about how proud she was of them.

On her last day of school before the wedding, Williams’s students threw her a party with cupcakes, enveloped her in a giant hug and gave her a book that had a piece of marriage advice from each girl.

“Mr. Berry, take good care of Miss Williams,” one wrote. “If you don’t, you’ll be sorry.”