"Listening and speaking are sensory partners of reading and writing," said Judith S. Sexton, director of the school, which also has a Philadelphia campus.
Researchers are still examining how well that theory holds up in the long term, as the first generation of children with cochlear implants enters adulthood. Some do well with the devices, which require surgery and extensive follow-up therapy, while others struggle to adapt.
What's clear is that the implants, two decades after they were first approved for children, have had a big effect on educating the deaf. The devices do not provide normal hearing, but they deliver electrical signals directly to the auditory nerve, enabling the deaf to perceive sound.
With the advent of newborn screening for hearing loss, deaf children are getting the surgery earlier than ever - in some cases even before the federally approved benchmark of 12 months - and evidence suggests they learn to speak better as a result. Meanwhile, with more deaf children in regular public schools, enrollments have declined at traditional schools for the deaf. That has raised concerns for some in the deaf community, a proud group that boasts a rich culture and does not necessarily see hearing loss as a disability needing to be fixed.
There are approaches between the extremes. At the Pennsylvania School for the Deaf in Germantown, 30 of the 220 students have implants, and all are taught bilingually, with some classes in English and some in American Sign Language. New Jersey's Katzenbach School for the Deaf in Ewing uses a technique called "total communication," involving the simultaneous use of speech and signs.
At the Clarke School, which is seeking approval for state tuition funding, teachers do not use sign language. This "auditory-oral" approach is also used by publicly funded "intermediate units" in Montgomery, Bucks, and Delaware Counties, which offer a mix of classroom and itinerant services. And Chester County sends some children to Clarke.
Few head-to-head studies have compared the approaches, and the landscape is complicated because deaf children are a diverse group, said Marc Marschark, editor of the Journal of Deaf Studies and Deaf Education.
"We cannot fall into the trap of making assumptions about which program works best," agreed Larry S. Taub, head of the Pennsylvania School for the Deaf.
Before implants, studies found that half of deaf people read below fourth-grade level, though many did well enough to attend college and have successful careers.
Children with cochlear implants seem to read better, on the whole, though some still struggle for a variety of reasons. It is likely that experts still have not arrived at the best way to teach both children with implants and those without them, said Marschark, a professor at the National Technical Institute for the Deaf at the Rochester Institute of Technology.
One long-running study followed 181 children who had gotten cochlear implants between ages 2 and 5. At 8 or 9 years old, 61 percent read at a normal level or above. (The figure among normal-hearing people would be 84 percent.)
By high school, 69 of the children had left the study, some possibly because their implants did not work well, and just half those remaining read in the normal-or-above range.
Still, the achievement was better than that traditionally seen in deaf children, said study author Ann Geers, a research professor at the Dallas Cochlear Implant Program at the University of Texas at Dallas. And with children receiving implants earlier and with better technology, early evidence is that reading scores are even better, Geers said.
Other experts say the advent of early diagnosis is perhaps more important than implants. Previously, hearing loss was sometimes not diagnosed until age 2 or older. Now it happens before newborns leave the hospital. In one method, a machine delivers a series of clicks into the baby's ears, and electrodes measure the auditory nerve's response.
Whether parents choose sign language, speech facilitated by implants, or some combination, deaf children are exposed to language earlier than ever.
"The important thing is language. There are a lot of ways you can get it," said Carol Knightly, clinical operations director of the Center for Childhood Communication at Children's Hospital of Philadelphia.
At the Clarke School, students get their language through listening.
To make life easier for them, the Bryn Mawr building was designed to minimize the echoes and background noise of a typical school. With acoustic-tiled ceilings and floors covered by carpet and sound-absorbing cork, Clarke has the muffled ambience of a recording studio.
Some of the students' speech is a bit hard to understand, but that's true for any group of preschoolers. While some wear hearing aids, most have cochlear implants.
Students are not taught sign language lest it detract from the mission of speaking and listening, Sexton said.
Marschark, the journal editor, said there was no evidence that signing hindered academic achievement, and it may even help, given that children can learn to sign before they talk.
Meanwhile, technology continues to improve, and to become more widespread.
The Food and Drug Administration started approving cochlear implants in the mid-1980s for adults, and in 1990 the first ones were approved for children as young as 2. That age has since been lowered to 12 months, and some surgeons will do the surgery even earlier.
An implant consists of a microphone and speech processor, worn outside the head, that transmit signals to a receiver beneath the skin. An electrode array then carries the signals to the auditory nerve. Users can learn to understand speech, though music is a challenge.
Newer hybrid devices, designed to let the user make use of any residual hearing, are being tested - including one in a trial in which the University of Pennsylvania is participating.
It is not clear what percentage of deaf children receive cochlear implants, but thousands of procedures have been done since 1990. Though most insurance plans cover them at least in part, implants cost more than $40,000, including postoperative services. Yet advocates say they are cost-effective in the long run because users often end up at a mainstream school, sometimes without need of an interpreter.
Some children with implants attend traditional schools for the deaf, but the technology does seem to be contributing to a decline in enrollment, along with a federal mandate that students be educated in the "least restrictive environment."
In 1993, more than 12,000 hearing-impaired children attended a separate school for the deaf, according to federal statistics that include children with all degrees of hearing loss. In 2005, the most recent year available, that figure was down to about 9,500.
Concerns remain that this trend will threaten the notion of deaf culture - a concept as deeply rooted as that of any ethnic group, with its own traditions, literature, social customs, and values.
Taub, the head of the Pennsylvania School for the Deaf, said he did not think there had been much effect yet, though he said parents of some children with implants had asked about the issue.
"They ask, 'Will they have a sense of belonging to either community?' " Taub said, adding that his school's bicultural approach addressed this.
Attitudes may be changing among the younger crowd that grew up with technology. Mercy Raudenbush, a woman from Millville, N.J., who wears an implant and attends the Rochester Institute of Technology, said her peers without implants accepted her.
"My deaf peers treat me equally," she said. "They are very respectful people."
Marschark, the professor, said many younger deaf people viewed implants as little more than high-tech hearing aids.
Some implant wearers may use the devices during class but turn them off in the dormitory, he said. Then, he said, it's back to the communication mode that defines the community: American Sign Language.
Contact staff writer Tom Avril at 215-854-2430 or firstname.lastname@example.org.