At Flower Hill Elementary School in Gaithersburg, teachers sometimes have to wait in line to use a bathroom.

The first batch of children eats lunch at 10:45 a.m. so that all 900 pupils can be fed before the school day ends.

And there is not much room on the playground, because 14 portable classrooms occupy two-thirds of the blacktop.

These are some of the side effects of the growth spurt of residential development in the upper part of Montgomery County -- a spurt that has meant that Flower Hill, which opened just two years ago, today enrolls nearly double the 500 students it was built to accommodate.

"Development has made it very difficult for our staff," said Sidney Hauser, a guidance counselor at the school. "It takes nerves of steel."

Hauser recounted tales of Flower Hill's cramped conditions yesterday to educators, parents and civic leaders who held a community forum to examine whether the county's economic development is hurting its schools.

The answer was an emphatic "yes" for most of the 80 participants at the meeting sponsored by a county group formed last winter called the Community Coalition for the Schools.

"The bottom line is that economic growth should not involve sacrifices in the quality of the schools," said Mark Simon, president of the Montgomery County Education Association, the teachers union that was among more than 30 civic groups that created the coalition.

"This county can afford, and the citizens want, improvements in the schools," Simon said. "The costs of rapid economic growth should not be made an excuse for not doing what needs to be done."

The county has begun trying to cope with the explosive growth by planning to build 19 schools in the next six years and by enforcing a zoning law that requires adequate schools and other public facilities to be in place before new development is permitted.

The supply of schools was a key factor the County Council considered when it approved its first Annual Growth Plan in June. In the plan, which is aimed at controlling the shape and rate of development, the council decided that no part of the county had a severe enough school shortage to warrant a moratorium on the building of houses.

But many participants at the forum doubted the ability of county government to keep pace with the development boom. They challenged the accuracy of past enrollment projections, and said they were skeptical that their schools will be easily able to absorb the rapid influx of students expected during the next several years.

Some questioned the wisdom of further growth, contending that the benefits to the county's tax revenue may be offset by the strain on county services, including schools.

"In recent years, we've assumed development equals progress equals milk and honey," said Allen Bender, president of the Montgomery County Civic Federation. "We've assumed if we did not compete for development, it would go to Fairfax {County}, and we couldn't let it go to Fairfax."

"We need to balance education policy and development policy," Bender added. "We don't want development dictating education policy."

But school administrators who attended the session indicated they were reluctant to try to block the path of developers.

"The school system's job in my view is not to say, 'No, you can't build,' " said Philip H. Rohr, director of facilities planning for the schools. "Our goal is to provide classrooms for the kids."

According to the school system's predictions, the number of students in Montgomery's schools will grow from 96,500 to 120,000 by 1994.

The boom is expected to be greatest in the upper part of the county, where enrollment is projected to increase 36 percent by 1993. But it is not restricted there. Enrollment is expected to grow by 10 percent during the next six years even in the county's southern section, which includes older communities such as Bethesda and Chevy Chase.

By the early 1990s, the pace of Montgomery's enrollment growth will exceed that of the baby boom days of the 1950s and '60s, according to Philip H. Rohr, director of the school system's department of educational facilities planning and capital programming.

With enrollment already swollen beyond what the schools can hold, especially in the northern part of the county, roughly 4,700 Montgomery students attend school in 188 portable classrooms, Rohr said.

At yesterday's meeting at Maryvale Elementary School in Rockville, coalition members said they intend to convey their reservations about the effects of development to the county's budget and planning officials, and to the County Council.