The second-graders in Caroline Peloso's class sat quietly through the film on sex abuse, but once the projector was off and the lights came on they raised their hands impatiently to share their own experiences.

One boy said his baby sitter had invited a man into the bathroom "to test my sister's bath water . . . and made her stand up. She didn't have any clothes on. It was weird."

The youngster told his class that the episode left him with the "uh-oh feeling," an indication of a confusing and frightening experience with an adult that teachers hope will help the children at Beverly Farms Elementary School in Potomac protect themselves from abuse.

The class discussion was an introduction to a ground-breaking curriculum unit on child sexual abuse in the Montgomery County public schools. It is used to teach children that strangers and "even people that live in your house," can hurt them with "bad touch" and to instruct them how to report sex offenders.

The program is the only full sexual abuse curriculum in use in the Washington area. It is one of the most organized, systematic efforts within the grass-roots network of parents, teachers and administrators that has developed nationally in the past year in response to the dramatic increase in the number of reported sexual abuse cases, according to educators and specialists on the subject. Other local jurisdictions are working to develop similar programs, and the National Education Association last month released a teacher training program on child sexual abuse.

Called "Safety, Touch and Me," the Montgomery curriculum is built on the concept that touch can be divided into "good," "bad" and "confusing" categories and that children have the right to refuse being touched. The point is made gradually, but it can cause some confusion because it does not explicitly say what is "sexual" about the abuse. Such confusion was expressed in Peloso's class last week concerning the last scene in the film: There is a young boy in bed crying. The shadow of a man is seen standing beside him and the man warns the boy not to tell anyone what has happened because the man could go to jail.

Some students said they did not understand how the man had hurt the boy. "We don't know. All we know is that he gave him the 'uh-oh' feeling," school counselor Sherry Shear told the students.

The subject contains some inherently mixed messages. For children who have never been victims of sexual abuse, said Shear, the scene in the film was mysterious. But for the child who is a victim, the connection is immediate, she said. Bringing up the subject could also make a child suspicious of harmless touch if not taught in a proper or thorough manner, say teachers who have talked about child abuse in classes.

To avoid confusion, the Montgomery County curriculum makes its points slowly and progressively. In the first lesson, children pass around and sift through a "feely box" filled with such objects as velvet, cotton balls, feathers and sandpaper to help them define what "touch" is and "that we have the right not to like some things we see, hear, taste, smell and touch," the curriculum states.

The lesson moves on to define the meaning of "private," and students are asked to "show where the private parts of their bodies are by showing the parts of their body their bathing suit covers." Later in the curriculum, students are asked to cut out pictures of people in magazines "to show what you think a sex offender looks like." This follows a lesson telling them that offenders are not necessarily ugly or "scary."

In a word-puzzle game, a student must find and circle such words as "obscene phone call," "exposer" and "flasher" after discussing their meanings in class. There is also a sexual-abuse case to analyze and students must be able to refer the victim, Ruth, to a parent or government agency.

The Montgomery County curriculum unit was funded by the Maryland State Department of Education. It was available to teachers last year but only a few teachers signed up. This year, training sessions have been requested by individual schools at a rate of one a week, said Sharon Gilder, who conducts the training course.

The increase interest comes as county officials report an increased number of suspected sexual abuse cases. Last month, the Montgomery County school system reported it had referred 200 cases of suspected sexual abuse and neglect to the county during the 1983-84 school year, double the number reported in 1979. The increase mirrors national and regional trends. In the Washington area, the number of suspected sexual abuse cases has increased between 10 and 50 percent since 1981, according to local child protection agencies.

Nationwide the number of suspected abuse cases reported between 1976 and 1982 increased 123 percent, according to the National Center on Child Abuse and Neglect. Approximately 6 percent of the 929,000 cases in 1982 were for sexual abuse. A 1981 study by the center found that professionals -- individuals working for local police, schools, courts and county agencies -- were reporting only about one-third of all the cases they knew about.

And a national survey conducted by the NEA revealed last year that uncertainty over legal responsibility has inhibited teachers from confronting the problem in a systematic way, said NEA President Mary H. Futrell.

"Teachers need to feel they aren't going to be persecuted or harassed" for reporting suspected cases, said Futrell, who also advocates that student teachers be trained in child abuse prevention and counseling before they are hired. In every state teachers are legally obligated to report suspected cases to the appropriate local agencies. Failing to do so can result in fines and even imprisonment in some states.

Marion Burkhalter, of Montgomery County's health department, and others say that teachers are the most obvious intermediary between the abused child and protective agencies because of the time they spend with students and the trust that develops between them.

The curriculum is not mandatory and parental consent is not required. School officials in Montgomery County report only a small number of complaints from parents who believe the subject is not appropriate for the classroom. Last week, a play on sexual abuse, "Hugs and Kisses," came under attack from parents in Prince William County. The Board of Education there voted to continue the performances scheduled at elementary schools around the county, but school officials in Fairfax County last year canceled the play after similar complaints.

Burkhalter said the course was developed for fourth-graders because they are at the most vulnerable age. "That's the age when they get a little more freedom, are more involved in the world," she said. Although only third- through sixth-graders at Beverly Farms Elementary School will use the curriculum, the teachers decided this year that it was worth bringing up the subject with all of the students -- using only the film in the lower grades -- in hopes of helping a few more.

As the second-grade class ended, one girl who had sat silently caught Peloso with a great hug, leaned up close to her face and said softly, "I want to tell you something."

Later she told her teacher that a stranger had approached her and that she had run home and told her mother.

"Of the few cases I've been aware of in the past," said Shear, "they might have occurred once, but they would not have reoccurred if the children had known how to deal with them."