Nine-year-old Jay Bayfield and his Herndon Elementary School classmate, Bernard Woolfley, were on their knees in the hallway measuring the distance between their classroom and a room two doors away.

"It's 18 meters and 8 centimeters," Bayfield said as he wrote the distance in on an assignment paper that asked the fourth-grade students to measure - in the metric system - among other things, the classroom size, the windows in the rooms, door hinges and body parts.

For Bayfield and Woolfley, it was just another school day. They are among thousands of area school pupils who are being taught the metric system in public schools this year. For, despite resistance to the metric system in some parts of the nation, school officials in the Washington metropolitan area are enthusiastically promoting it.

In Fairfax County, a metric education specialist has been appointed to instruct teachers in teaching the metric system this year and to prepare classroom lessons. In Prince William County, elementary school teachers are attending two-day workshops where they learn the metric system ("metric," for short) and school officials there are planning to apply for a federal metric education grant.

In Arlington, the only new measuring devices being purchased are those that measure in metric. In Maryland and the District, officials are stressing that their students be taught metric in practical ways: such as teaching them to measure milk cartons and desks. In some home economics classes students learn to cook by using recipes that have measurements in metric. Some schools have converted track and field measurements to metric.

"We've taken the position that metric is coming," said Frank Miller, mathematics supervisor for Arlington schools. "We've got to get ready."

"A big push for the metric system is coming from industry," said Miller.General Motors and IBM are among numerous large corporations that are well along in their metric conversion programs. Speed on many new cars is measured in kilometers per hour as well as the traditional miles per hour. Many grocery items now display metric measurements. Some doctors now give height and weight in metric measurements.

School officials cite these new developments as the need to prepare students for the future.

"Students are taught to think metric," said Julia A. Kriss, metric education specialist for Fairfax schools. "There is no conversion between the two systems," she said. "It just becomes complicated when you try to convert from one system to another."

Teacher guidelines emphasis: "Don't convert. Learning the metric system is similar to learning a foreign language. The goal is to 'Think Metric' and 'Do Metric.'"

Sometimes thinking metric in a nation that still relies on the English system can be difficult as one Herndon Elementary School fourth-grader found out.

After measuring the size of Betty Lowenbach's fourth grade classroom, a student remarked: "The classroom is 9 meters and 21 inches."

"You mean 9 meters and 21 centimeters," said Jay Bayfield as he corrected the slightly embarrassed girl.

Lowenback had her students measuring in metric everything from their fingers, arms and necks, to tiles in the classroom floor.

"All of these activities are for them to experiment with," said Lowenbach. "It gets a little chaotic, but it's better for them to do the actual measuring than for me to stand up her and talk to them."

She said her students appeared to have very little problem absorbing the metric system.

"At first, I thought it was complicated," said 9-year-old Robbie Lorey."Now it's easy. If you just know how to count by 10, you know the metric system . . . 10 decimeters equal one meter, 100 centimeters equal one meter, 100 centimeters equal one meter and 1,000 millimeters equal one meter . . . I think it's really the simplest form of measurement."

"I don't really hate it and I don't really like it," said Adriene Baker, a fourth-grader. Baker said her parents had told her that she would have to teach them the metric system.

"Teachers are having more of a problem than anybody else because we're learning it too," said Lowenbach, who initially approached the metric system with reluctance. "When I can learn it, I will be all for it," she said.

Next door, teacher Charles Henrichs had his third-and-fourth-graders make their own metric sticks out of strips of yellow and green paper. Each student was given a thin ruler that measured 1 decimeter. The strips of paper were to be measured in decimeters and then pasted to a thin white piece of paper until they formed a meter.

Kelli Jewell, an 8-year-old, stared puzzingly at the strips of paper. "I don't know how long a meter is," she said to the teacher.

"How many decimeters make a meter?" asked Henrichs, a retired military officer.

"Ten," Kelli replied.

"Then you don't cut it (the meter stick) off until you get how many?" Henrichs asked.

"Ten!" Kelli beamed.

School officials say the metric system generally has received positive responses from parents. "Wherever the parents have been educated about it, they have been very receptive," said Thomas Rowan, mathematics coordinator for elementary schools in Montgomery County. He noted that "some parents complain that we're going too fast."

However, Rowan said the state of Maryland set up a bylaw several years ago that metric had to be taught in all schools by 1980. Most mathematics and science classes on the secondary level always have taught to some degree the metric system, officials said.

Area school officials say most of the resistance to the metric system has come from adults who are used to the English system.

"People are creatures of habit," noted fairfax County's Kriss, who said most teachers are uneasy in their initial confrontation with the metric system in teacher workshops.

"We try to reassure them that if you can multiply and divide by 10, it's easy," she said.

Fourth-grader Robbie Lorey said his parents think the metric system "is a waste of time. They think it's really not important since they didn't have to learn it in school. But I think it's worth knowing."

"They will catch on," said his classmate, Jay Bayfield.