SULTAN — No talking is allowed in Sherry Knox’s advanced American Sign Language class at Sultan High School.

Even as they were returning to the classroom after lunch, students were shushing each other the moment they stepped inside.

Yet communicating is still allowed — so long as they speak only in American Sign Language.

“It’s not easy not being able to talk,” said junior Carrie Hayes, 16. “But it’s good practice because it would be rude to (speak aloud) to a deaf person.”

Knox has been teaching the class at Sultan High School for 10 years. Hers is one of only a few that offer ASL in high schools, where it is taught as one of the foreign languages, along with Spanish and French, which students are required to take.

Knox’s classes are a popular choice. About a fifth of the school’s 568 students are taking one with Knox this year.

This is Knox’s first job as a teacher. She started learning ASL 24 years ago to be able to speak with her deaf son.

At the time, she said, she was told two-thirds of parents with deaf children never learn to sign. “I said, ‘No way that will happen with my son,’ ” Knox said.

She worked with deaf middle school children as an interpreter and tutor from 1992 to 2000, when the family moved to Sultan. Her son needed an interpreter at Sultan High School, but there were none. So she became his school interpreter.

Her son, Nathan Underwood, is now 26 and studying culinary arts at The Art Institute of Seattle.

According to a 2009 state report, 73 high schools and 18 community colleges in the state offered sign language classes. Among the schools offering the classes this year are the Sky Valley Education Center in Monroe, and Everett Community College. Everett School District discontinued the classes this school year because it was difficult finding qualified teachers, spokeswoman Mary Waggoner said.

In 2001 the school district in Sultan asked Knox to teach a sign language class. She earned her certification the next year, and the program has grown ever since.

On Wednesday, she made her advanced class sit in a circle and sign a sentence with words they had on their flashcards. After that, they formed groups to survey each other about their homes.

They were only allowed to speak five minutes before the end of the class to clarify anything that was not understood.

The no-talking rule helps students focus on what they are saying with their hands, Knox said. “It helps them learn the syntax and sentence structure. If they are talking, they can’t do that.”

Knox’s next class was for beginners. It was a special day for them, because it was the last day they were allowed to speak in class.

“It’s going to be a struggle, but we’ll get through,” said sophomore Ariel Acob, 15.

All of her students are scheduled to be silent for an entire day in the spring. That will help them better understand how a deaf person lives, Knox said.

“It gives them an opportunity to face some of the communication barriers deaf people face,” Knox said.

The classes also have a community service aspect. This year, the students are doing a food drive to help the Sky Valley Food Bank and are adopting two families to provide them with gifts and food during the holidays, she said.

For senior Sam Cotterill, 17, learning sign language has helped him connect with his deaf uncle.

“I didn’t know him before,” Sam said. “Now, I am learning the things he likes to do and what he was like as a kid.”

Alejandro Dominguez: 425-339-3422; adominguez@heraldnet.com.