A red and black Northwood High School banner still hangs on the wall of Annette Lane's bedroom, but when her senior year starts next week, she will board a bus and head for Montgomery Blair High School instead.

Northwood, which Lane attended for three years, was closed by the Montgomery County Board of Education last June, despite the bitter opposition of residents of that area of Silver Spring. Most of Northwood's students and staff were divided among three other high schools.

"Right now it's kind of unsettling. We're just waiting to see what the year has in store for us," said Lane, an honors student at Northwood. "It's really a frightening experience to know you have to start all over again."

The aftershocks of Northwood's closing are among the emotional issues that will be faced by the Montgomery County School system when more than 94,000 students pour into classrooms next Tuesday.

After a decade of declining enrollment, this will be the second year in a row that the Montgomery school system, third largest in the state and 20th largest in the country, will show an increase in new students. More than 2,400 new enrollments are expected, compared with 769 last year.

Based on past experience, school officials said the actual number could top 2,500 once official enrollments are tallied Sept. 30.

"Generally our projections are a little conservative," said school spokesman William Henry.

The projected increase is the largest in 16 years and the second largest in school history. In the 1969-70 school year, a record 3,522 new students enrolled, school officials said.

The surge is expected to overcrowd several schools, especially those in the fast-growing Gaithersburg-Germantown area of upper Montgomery County. Portable classrooms will be used in unprecedented numbers, and the school system will start the year with 600 more teachers, nearly half of whom have been hired to handle the influx of new students.

With a record $437 million budget this year, the school system has also hired 46 new elementary school teachers, 10 junior high teachers and three high school teachers specifically to reduce class sizes, school officials said.

In all, the schools will employ 6,600 teachers this year at 153 schools, officials said.

Last year, the school system experienced a shortage of qualified substitute teachers, but this year the problem has been addressed, said Mark A. Simon, president of the Montgomery County Education Association. The schools have lined up 2,000 substitutes this year, compared with 1,700 last year, he said.

For the first time since 1975, the school system will open two new elementary schools in Gaithersburg and Germantown to accommodate the children of families buying homes in the new subdivisions there. Lake Seneca, the Germantown school, will be overcrowded the day it opens, said Anne Briggs, coordinator of school facilities.

Thirteen schools will use portable classrooms -- modular units like those used for housing -- for the first time this year, nearly doubling the number that have them, said H. Philip Rohr, director of construction and capital projects.

About half of the 96 portable classrooms to be used this year have been placed, but 27 additional units will not arrive in time for opening day, forcing some schools to hold classes in auditoriums and other rooms, Rohr said. The units are expected to arrive in three weeks, he said.

At the same time the school system faces near-record growth, changing development patterns and a sharp enrollment decline in older, urbanized communities in the lower part of the county are threatening the future of schools in Rockville and Bethesda.

School Superintendent Wilmer S. Cody last week urged the school board to close either Walter Johnson High School in Bethesda or Charles W. Woodward High School in Rockville, consolidating students in one school. He also recommended closing Cabin John Junior High School in Rockville and transferring its students to Hoover Junior High School.

The recommendations were contained in a report that included more than a dozen other proposed changes in attendance patterns to balance enrollments in the 45-school district, known as Area II, encompassing Rockville, Potomac, Bethesda, Chevy Chase and part of Wheaton.

The superintendent's report almost assures that the first three months of the new school year will be dominated by the kind of emotional debate that marked the Northwood High closing, in the view of parents whose children would be affected by the changes.

The school board is scheduled to hold public hearings on Cody's recommendations in early November and will make a final decision on the report at a special meeting Nov. 19.

The school board must also deal with overcrowding at Highland View, Montgomery Knolls, New Hampshire Estates, Oak View and Rolling Terrace elementary schools, which are in the Blair High School cluster in Silver Spring.

Cody proposed a solution to the overcrowding earlier this year, but it touched off citizen protest because it would have increased the number of minority students at some of the schools, said Cheryl H. Wilhoyte, director of magnet programs.

New Hampshire Estates and Rolling Terrace had enrollments at more than 100 percent of capacity last year and each now has three portable classrooms to accommodate excess students. Minority enrollments at both schools now exceed board guidelines.

Last week, Cody proposed building additions to New Hampshire Estates and Rolling Terrace elementary schools at a cost of $9.2 million to handle the overflow of students and to provide space for optional magnet programs that are designed to attract whites.

Potentially, the plan could reduce the minority population at New Hampshire Estates from 91 percent to 67 percent and at Rolling Terrace from 79 percent to 68 percent, officials said. However, minorities would increase from 42 percent to 44 percent at Oak View, according to the report.

A new academic magnet program, focusing on reading and language arts would be developed and operated between New Hampshire Estates and Oak View to draw white students to the schools, Wilhoyte said.

A hearing on the latest proposal has been scheduled for Sept. 18.

Although growth has been the biggest issue facing the school system recently, academic achievement is likely to eclipse that this year because of growing pressure from parents to boost the performance of minority students and because more stringent, state-mandated graduation requirements go into effect this year.