Amil Keller, 11, a sixth-grader at Meadow Hall Elementary School in Rockville, began one recent school day by feeding Abraham and Mack - two mild-mannered goals - and bringing water pumped from a well to a litter of overweight rabbits.

At the sound of an old-fashioned school bell (the big, clanging kind that has to be pulled with a rope) Amil's real schoolwork began.

He had to go out to an open field with his compass and get from one point to another, using the compass as his only aid.

He also had to measure the depth and width of a section of Rock Creek and to determine, through a quick chemical test, the acidity level of the water.

Meanwhile, some of his fellow students were learning about how owls live as they pet a living owl held out to them by their teacher. Still others were watching a swarm of bees make honey.

Amil's classroom that week was the Rock Creek National Park, where the Montgomery County school system has built the Lathrop E. Smith Environmental Education Center in Muncaster Mill Road near Lake Needwood. Sixth grades from various schools throughout the county spend a week at the center while other grades up to senior high school come for a day at a time.

The only classrooms at the Smith center are the rolling fields and wooded areas of Rock Creek Park. The only textbooks are the creek itself, the earth and the sky.

Montgomery County's extensive outdoor education program reflects a growing trend among school systems nationwide to get students outside the classroom and have them experience first-hand the types of things they read about in science, georgraphy and history books.

While nature trips are nothing new in education, few urban schools systems or those like Montgomery County's which is in a large metropolitan area, had formal programs in environmental education until the 1970s.

Now, educators say, getting kids out of the classroom to "learn by doing" is fast becoming the rule rather than the exception in education.

In New York City, for example, about 30,000 public school students spend at least one day of the school year learning out of doors, according to Irwin Tobin, of the New York City Board of Education.

Outdoor education "is a successful device for motivating students. Kids look forward to it. It facilitates the learning process," said Tobin.

Environmental studies came to most schools as a result of the ecology movement of the late 1960s and early 1970s, but the concept is used by many school systems as a social tool.

The District of Columbia's week-long outdoor education program, for example, serves as a means of mixing students from predominantly white schools with students from largely black neighborhoods, according to Lucille Leisner, director of outdoor education for the D.C. schools.

District of Columbia fifth-graders spend a week in the Catoctin Mountains in western Maryland where they study the natural surroundings. The students' experience of living together for a week "really does seem to alleviate racial barriers," Leisner said.

"The theme of the entire week is inter-relationships . . . the inter-relationship that go on in nature . . . We blend this in with the whole cultural thing" to show students how even different cultures inter-relate, Leisner said.

The popularity of outdoor education among teachers and principals is widespread, according to Joe Howard, director of Montgomery's program, "because they saw how well kids respond to learning out of doors. And the kids are enthusiastic about it, too. You don't have to sell the kids on it."

"It's funner," is the way sixth-grader James Boline summed up the way he feels about learning history, science and geography in the Smith outdoor center.

A former principal, Howard keeps this quote from Thoreau, which sums up the idea of outdoor education, on his desk: "What is it then to educate but to develop these diving germs called the senses?"

A group of 77 students from Four Corners Elementary School in Silver Spring, where Howard was principal, was the first group of youngsters to participate in an outdoor education program in Montgomery in 1963. But the county's program did not blossom fully until the opening of the Smith Center in 1974.

The school system also sends thousands of students to three rented out-of-county camp sites each year.

The Montgomery teachers try to relate what their students learn in the classroom to what they experience at the Smith center. They encourage students to use that experience. And, they say, they try to show the students how everything they learn about is inter-related.

When the students return from a walk in the woods, they usually draw what they have seen or paste up some of the objects they collected along the way. The Meadow Hall students wrote haiku Japanese-style poetry about their experiences in the woods.

All the students who visit the Smith Center keep a daily journal.

The outdoor education program in Montgomery, is linked to another "learning by doing" trend in education called "experiential" education. These activities thrust youngsters into new experiences to help them build self-confidence and develop a sense of cooperation.

Youngsters who visit the Smith Center might be asked to swing from one side of rock creek to the other on a rope, scale an eight-foot wall, or climb a 20-foot ladder in order to reach a branch on a tree.

Though there are dangers inherent in sending children especially from the city - into natural surroundings, only one child has ever been injured at the Smith Center - a sixth-grader who broke a capped tooth, Howard said.

Since then, all parents are asked to pay 25 cents to insure their child.