While Howard County teacher Jutta Derringer was drilling her class on French verbs, she wheeled around and wrote a student's name on the blackboard. A moment later she placed a check by it.

Without exchanging words or disrupting the lesson, she had just disciplined the student for talking out of turn and assigned him to 15 minutes of detention.

The system Derringer used to maintain order in her ninth-grade French class at Howard County High School is the cornerstone of "assertive discipline," a technique that uses elements of behavior modification -- positive and negative reinforcement -- to quell classroom disruptions by unruly students.

Assertive discipline is spreading across Maryland, as it has been strongly embraced by the 35,000-member Maryland State Teacher's Association. The organization has been actively promoting its use since last spring.

The rules of classroom behavior and the consequences for violating them had been carefully explained to Derringer's students on the first day of school. Parents were also informed in letters sent home with their children.

Now, there was no need to repeat the rules or disrupt the class with a time-consuming scolding.

"It works beautifully," said Derringer, one of about 20 Howard County teachers using assertive discipline on an experimental basis this year for the first time at Howard High, one of the county's most trouble-prone secondary schools, and at an elementary school.

The approach was developed in 1976 by Lee Canter, an Orange County, Calif., school counselor who formed his own consulting firm and now works full time promoting the concept, said Kathy Winberry, marketing director for the firm, Canter and Associates.

Canter's book on the subject is in its 14th printing, with 500,000 printed thus far, and the firm's 20 full-time consultants have trained more than 350,000 teachers and administrators in more than 30 states, Winberry said.

Although MSTA officials have no exact figures, they say teachers in Anne Arundel, Baltimore, Howard, Prince George's, Carroll and Washington counties are known to be using assertive discipline in their classrooms.

Teachers in St. Mary's, Kent and Calvert counties have requested training materials from the union,added James W. Spencer, assistant executive director for research. There is no information about use of the program in Montgomery, which has not made any moves to introduce it.

Despite its apparent, skyrocketing popularity, assertive discipline has not been a universial success in the state.

In an out-of-court settlement last week in Anne Arundel County, five students were awarded monetary damages because of an 1981 incident in which a teacher using assertive discipline had placed them in sometimes darkened utility rooms.

Attorneys for the children had sued, charging that the punishment was cruel and unusual. Canter has said in the past that his program does not recommend placing children in isolation.

Critics say the Anne Arundel case suggests that teachers may not be getting proper training in assertive disipline techniques, and may be improperly applying them in other parts of the state as well.

Outside of broad guidelines, the State Board of Education traditionally has delegated the issue to local boards, which often leave the question of classroom discipline up to administrators at individual schools, according to state superintendent David Hornbeck.

In the Howard program, teachers learned assertive discipline techniques at a summer workshop using text books, films and other materials supplied by Canter's firm, said assistant Howard High principal Mary Day, who is overseeing the experiment.

"In the classroom, we only say two things," she said. "A teacher has a right to teach and a student has a right to learn."

Each teacher has drawn up a list of five classroom rules and has attached a specific consequence to "In the classroom, we only say two things. A teacher has a right to tech and a student has a right to learn." -- Assistant Principal Mary Day each if they are broken. The rules are enforced by a discipline plan that begins with a warning: the student gets their name on the board.

If the disruptive behavior continues, check marks are added to indicate a specific punishment.

One check is 15 minutes detention; two is 30 minutes detention; three is dentention plus a phone call to parents; four is detention and a parent-teacher conference and five is referral to the principal, Day said.

"You have rules and you have consequences, and the students and parents are made aware of what they are," Day said.

"The key is that these rules and consequences are applied consistently," she added.

The program so far has been well received by the teachers who are using it.

"They don't have to ask what happens if they come in late, they know, so the discussion on behavior is limited," said Mary Coates, a language teacher.

"I've always considered myself assertive, but it has changed my philosophy on how to approach kids in terms of expectations," said Earth science teacher Dave Vezzi.

Robert Ryan, 15, a sophomore in Derringer's class, said of the discipline technique, "It helps. Last year, the teacher would say something and the kids wouldn't listen."

Another key element is positive reinforcement.

Teachers are encouraged to praise students when they do well and to inform their parents by sending home notes. One teacher awards classes a special treat, such as a party, if they go for two weeks without getting names on the board.

"What I like best about it is I don't have to go home grumpy," said Coates. "I don't have to say anything negative on most days so I don't go home in a negative mood."