When one boy arrived, he would utter only two words: GI Joe. Now, he's holding conversations.

A little girl chose not to say anything at all. Now, she's speaking softly.

Another girl was so aggressive that she refused to take instruction and constantly threw temper tantrums. Now, she's calmed enough to be ready for public school.

These are three success stories from the Chatsworth School, one of six "special" public schools in Baltimore County and 48 in Maryland that serve about 7,200 children with severe disabilities.

Every educator's goal is to give children with disabilities a chance to flourish in a mainstream school. But some children's problems are so severe that they need attention that public schools just can't offer.

For those children, there are special schools. Some help the severely retarded or profoundly handicapped. Others, like Chatsworth, are for the learning-disabled, speech-impaired or emotionally disturbed.

A look at Chatsworth provides some insight into how these schools do their job and how parents decide if their child belongs in a restrictive setting where all the students have special needs.

Tucked in a corner of northern Baltimore County, in the 200 block of New Avenue in Reisterstown, Chatsworth School enrolls children

as young as 3 months and up to 11 years old.

Chatsworth's enrollment is a little more than 300, but at times it has grown to 400 because the public school must accept every " child who needs help and lives within its boundaries.

"These are children who are not somewhat learning-disabled but severely disabled," said Suzanne Ockun, the principal.

Often, she said, the children have multiple needs. They may need help with reading, learning to speak, or developing their motor skills. Some need the help of psychologists and, in a few cases, a student's behavior has deteriorated to the point of crisis.

Parents who decide to enroll their children in special education schools often do so at the suggestion of medical and education specialists, a step that requires the heart-wrenching admission that one's child is not progressing normally.

"Parents generally know when Johnny is not right," Mrs. Ockun said. "They notice that their children are not like the others."

Barry H. Willen, whose 6-year-old son, Josh, attends Chatsworth, has been in that position, and his experience is typical of what families go through.

"He was in a private nursery school, and the teacher brought it to our attention," Mr. Willen said.

Josh stayed to himself and exhibited impulsive behavior. His teacher thought he might have a learning disability and suggested that the Willens consult a physician.

"We were not too thrilled about it," Mr. Willen recalled.

Nevertheless, the family made an appointment with a pediatrician whose specialty was diagnosing and treating learning disabilities. "He recommended that we go to Chatsworth for an evaluation," Mr. Willen said.

Josh was 4 years old when he found himself being evaluated by the specialists at Chatsworth. His parents were told he had attention deficit disorder -- difficulty concentrating -- and other learning disabilities.

Josh is now in his second year at Chatsworth, and his father hopes it will be his last.

Josh's neighborhood school is Reisterstown Elementary, and for the most part he will be attending regular classes when he leaves Chatsworth. But he will be given extra help in reading and math.

Linda Weifenbach's 7-year-old son, Derek, was originally believed to need more help than even Chatsworth could offer. "He was diagnosed as being autistic and retarded when he was 3," Mrs. Weifenbach said.

She insisted that her son was not retarded but had a severe language problem. About two years ago, the experts concluded she was right, and Derek was transferred from a school for the severely retarded to Chatsworth.

"A child who was once believed to be retarded is now doing fractions and reading on the first-grade level," Mrs. Weifenbach said proudly. She believes the day will soon come when Derek is ready for a neighborhood school.

That is the purpose of Chatsworth, Mrs. Ockun said. "The goal of this school is to get children in the least restrictive environment. When we see that they are ready . . . they are out of here."

Of course, not all students improve enough to return to neighborhood schools. In a typical year, about one-third of Chatsworth's students leave for less restrictive settings, Mrs. Ockun said.

The earlier a child receives help at a special school, Mrs. Ockun said, the better his chances for leaving.

The school coordinates individual attention for children with the regular county curriculum. Therapists work with the children and offer ongoing training for the staff and workshops for parents.

Chatsworth is able to offer such intense help because of its specially trained staff and because a typical class has from six to 10 students and two teachers.

In neighborhood public schools, an elementary school student may find himself one of about 25 children in a classroom attended by one teacher and sometimes a teacher assistant or parent volunteer.

It costs more to educate a special education student because of the expense of paying specialists such as speech and language therapists or psychologists and the smaller teacher-pupil ratio.

The average per pupil expenditure in Baltimore County this school year is $5,355. School officials would not estimate the cost of educating a special-education child, but a few years ago XTC they put the cost of educating a severely handicapped child at more than $12,000.

"It is obviously more expensive," said Robert Y. Dubel, the Baltimore County schools superintendent. "But it is well worth the investment in these students. It is the compassionate thing to do."

The extra attention is behind the success stories.

When the aggressive 5-year-old girl who constantly threw temper tantrums came to Chatsworth last year, she was evaluated by a psychologist and placed in a class for emotionally disturbed children.

Each time the girl "acted out," she was made to sit in a corner away from the other children, where a staff member talked with her until she was in control. When she quieted down, she rejoined the class.

Teachers focused attention on the girl when she was not acting unruly, offering constant praise during those moments. She had to earn the time to play with games or puzzles by behaving appropriately.

Teachers telephoned the girl's parents often with updates on her progress. Gradually, the child began to act out less, and now she's able to handle a day in class as well as other children.

Nancy Stem, who teaches 6- and 7-year-olds, remembers the boy "who said nothing but 'GI Joe' when he came here."

He is speaking normally now and attending his neighborhood elementary school, where he takes some special education classes, she said.

Both he and the girl who arrived refusing to speak at all broke the language barrier by spending time with Chatsworth's speech and language specialists individually or in small groups.

Tim Carr, who teaches emotionally disturbed children on the fourth- and fifth-grade levels, says successes are counted in small increments. He spoke of a boy who could not stay in a class without throwing things. The child is in his second year at Chatsworth and improving.

"He's keeping his head above water," Mr. Carr said.

As for Chatsworth's students, they may not be aware of all the extra help they are receiving. To them, it's just a school where they go five days a week.

Josh Willen, now 6, exhibited the normal attention span of someone his age when talking about what it was he enjoyed about Chatsworth -- his math classes.

"It's not hard for me," he said.

"I like the smaller classes," said John Greene, 9, who has been at Chatsworth for a year.

Beth Bafford, 10, in her seventh and last year at Chatsworth, rattled off "spelling, reading, social studies and English" as the subjects she most enjoyed. "I don't like math," she concluded.

She looks forward to going to Johnnycake Middle School next fall but says she will "miss all my teachers."