Sarah Garvin and her dog, Satin, are a team. When Sarah, 15, a special-education student, goes to the doctor, Satin goes, too. At Sarah's therapeutic horseback-riding class, Satin waits outside the ring. During Sarah's elementary school years, the dog accompanied her to class several days a week, and the principal even introduced the 60-pound black Labrador retriever mix as "our new staff member."

But Satin, a trained assistance dog, is not allowed at Sarah's current school -- H.H. Poole Middle School in Stafford -- under a long-standing policy that bans most animals. That decision has focused attention on the question of how far a school system should go in meeting the needs of disabled students.

John and Melodee Garvin, Sarah's parents, asked that Satin be allowed to attend school one hour a week to help Sarah, who has Down syndrome and juvenile rheumatoid arthritis, in her speech pathology class. But school officials said no, and a mediator, who was brought in after the Garvins challenged the decision, also refused to admit the dog.

"These dogs are welcome anywhere else," Melodee Garvin said. "I've never been anywhere where Satin has been turned down because she's a dog. Sarah's dentist, in fact, when she has an appointment, sends her a reminder card that says, 'Bring Satin, too.' "

The first reason school officials gave for refusing the request was "dog dander," Garvin said. "Then it was, 'Sarah is doing well and needs no special accommodations.' "

But the Garvins see Satin as an additional resource that gives Sarah confidence and improves her learning skills. They say that Sarah, who has speech problems, speaks more clearly and authoritatively when she is giving Satin commands. Sarah's movements are slower because of the arthritis, and the dog is trained to take off her socks and to open doors for her by tugging on a towel tied to the door handle.

Stafford County schools spokeswoman Valerie Cottongim said she cannot discuss a case involving a specific student, citing privacy laws. Currently, she said, there is one service dog accompanying a student in the public schools.

The decision to permit or ban an animal is up to the school principal, who is given guidelines by the school system, Cottongim said. Under those guidelines, a dog could be permitted if it was required for a student "to receive benefit" from a special-education program, if the animal was used as a teaching strategy or it was needed as comfort or treatment after a traumatic event, she said.

"When we're looking at an animal on school property," she said, "we have to consider the needs of all the children and the health and safety of the students and staff. . . . A school is not the same as a restaurant or public place. We're not a public accommodation. All the children have to be there; they can't leave if there's something causing an issue."

Sarah met Satin in November 2001 through a national nonprofit group called Canine Companions for Independence. The organization, founded 30 years ago, has placed about 2,300 trained dogs with disabled people, according to regional program manager Ellen Torop.

Torop said that periodically, one of the group's dogs is denied access to a place but said usually it is a case of a business owner needing to be "educated."

Sarah and her mother spent two weeks at the organization's regional center at the State University of New York in Farmingdale, learning how to take care of a service dog and how to use its skills. At the end of the period, they were matched with Satin, who had been trained since a puppy for the job and knows 50 commands. Satin's sister, Sheba, ended up at a children's hospital in Brooklyn.

When Sarah received her dog, she was in a wheelchair because of her arthritis, but new medication has enabled her to walk on her own. She and Satin quickly formed a tight bond.

"It's funny. She never liked dogs to kiss her. Satin's the only one she allows to lick her face," said Rachel Garvin, 27, a special-education teacher in the Stafford County schools, whose career choice was inspired by her younger sister.

Sarah, who has shiny red hair and laughs a lot, enjoys school, her mother said. Socially, she does well, and she is constantly working on her reading and math skills. She is on swimming and bowling teams for Special Olympics, sings in the school chorus and looks forward to turning 16 in January. She wants a cake with a heart and a princess on it, she said.

She also enjoys showing visitors that she is Satin's mistress. "Satin! Come!" she called out on a recent afternoon at her Stafford home in a clear, peremptory voice, patting her knee three times. The dog hurried to her side and looked up at her expectantly. Melodee Garvin said Sarah is forced to speak in a way that Satin can understand, and "the carry-over into other areas of communication" is encouraging.

Satin had no problems attending Winding Creek and Kate Waller Barrett elementary schools in Stafford County, her mother said. Melodee Garvin would bring Satin to school and stay there during the classes; under the rules of the Canine Companions program, Sarah needs an adult "facilitator," such as her mother, to accompany her and Satin. Garvin said she also was prepared to perform that duty at H.H. Poole.

Advocates for the disabled who have heard of Satin's rejection have advised the family to seek an attorney. But Melodee Garvin is not sure about that.

"We hesitate going to a lawyer, because this is something they should do because it is good," she said. "They shouldn't be compelled to do it."

Sarah Garvin and her assistance dog, Satin, a Labrador retriever mix who responds to her commands.