When Montgomery County opens the doors of its 177 schools next week, the theme will be smaller is beautiful. And in this case, being smaller is necessary.

Since 1972 the county's public school population has dropped from 126,000 to a projected 95,000 this year and everything from the buildings to the textbooks will continue to shrink to fit. Federal, state and county budgets also have been shrinking.

Budgets and enrollments are not the only areas tightening up. The third year of a conservative majority on the school board promises a further tightening of academic policy at the high school, and possibly elementary school, level. And, in the name of a return to "neighborhood schools," the board will consider drastic alterations to what is considered one of the nation's most progressive voluntary school integration plans.

Smaller and tighter means:

* Argyle, Leland and North Bethesda junior high schools, Broome Middle School and North Lake Elementary closed their doors forever last June because of declining enrollments and aging buildings.

* Superintendent Edward Andrews will seek board approval of plans to close an additional 31 schools through 1986. A foot-high stack of alternative plans has been submitted by concerned parents, promising a stormy series of public hearings throughout October and November before the board takes a final vote in November.

* The school board voted this week to make final exams, now mandatory for all academic courses in high school, count as 20 percent of the final grade for each semester's work.

* Seventy-six administrative positions have been slashed as of last July 1. The number of area offices in the decentralized system has been reduced from five to three, boosting the number of schools in each area from 45 to 60.

* Minority community leaders have stiffened resistance to policy changes made by the conservative majority on the seven-member school board. The changes include allowing an increase in the acceptable percentage of minority students in schools and the disbanding of the Minority Relations Monitoring Committee.

Reagan administration budget cuttters are also playing a part in this year's tight budget theme. Federal impact aid, which peaked at $6.2 million in the years from 1970 to 1976, was only $2 million last year. This year, according to longtime school spokesman Kenneth K. Muir "it's gotten so chancy that we haven't even budgeted it as revenues in the past few years."

Federal aid targeted to ease school integration problems also has been cut from $531,000 last year to $312,000 expected this year. The money provides staff for special counseling in classrooms with high minority populations as well as a special arts program designed to attract whites to Silver Spring's Page Elementary, which otherwise would have a high minority enrollment.

Loretta Webb, head of the Quality Integrated Education program, noted that "Fifty percent of the students that had been served will not be served. We've lost 50 percent of our staff."

Cuts in federal assistance also will raise the cost of elementary school hot lunches from 65 to 80 cents, secondary school hot lunches from 70 to 85 cents, and a la carte items will be hiked 20 percent. The standard half pint of milk will go from 15 to 20 cents and even the reduced rate lunches for poorer students will be doubled from 20 to 40 cents.

Meanwhile, back in the classroom, Montgomery students, already among the highest scoring in the country on standardized tests, face the prospect of becoming the most tested. Last year the board mandated a controversial policy that high school finals be given by each academic department. This week board members ordered that exam grades count for 20 percent of the final semester grade. The board also will consider extending uniform final exams in math, history and science down through the kindergarten level, said board member Marian Greenblatt.

Some parents and students have expressed concern about the focus on tests.

"The children are actually being tested to death, if you want to know the truth," said one county PTA official.

Overriding these concerns, school closings will be the biggest issue in Montgomery education this fall, and hundreds of parents will battle to keep open their neighborhood schools. Ironically, while the school board hopes to limit busing for integration, some students will be bused up to seven miles each way to their new classrooms because of necessary school closings.

Tricia A. Ritter, a seventh-grader who had expected to attend Argyle Junior High, will now travel seven miles from her home in Wheaton to Colonel E. Brooke Lee Junior High in Silver Spring. She said she is not looking forward to the bus trip but believes "I'll make new friends." Ritter, along with about 400 seventh- and eighth-graders from Argyle will attend Lee, where there already are about 340 students.

Barbara A. Ritter, Tricia's mother, said she is more upset than her daughter is about the change because Tricia "used to leave the house at 8:40 a.m. to walk to school and now she'll have to leave at 8 a.m. to catch a bus. She'll also get home much later."

"The thing that hurts the most is that we had a good argument not to close the school, but the decision was made for political reasons. School board members Peyser, Zappone and Greenblatt all live in the Lee area," charged Tricia's father, Albert D. Ritter. He said Argyle is a larger and newer school than some others, and there is more potential for population growth in the Argyle area than in the Lee district.

Unlike their neighbors in Wheaton, parents and students from the North Lake Elementary district in Rockville seem to face considerably fewer problems making the transition to Flower Valley Elementary, also in Rockville. Much of the staff and even North Lake principal Carolyn Ray will accompany the students to their new school.

When about 240 North Lake students enter Flower Valley in September, the student population will double, Ray said, but she doesn't anticipate any problems because "There are so many similarities between the two schools and the two communities."

The trauma of changing schools is in store for hundreds more parents and students over the next few years. School officials have set aside 13 evenings in October and 13 more in November for the work sessions and public hearings on the closing plan. They promise to draw big crowds.

"A number of those weeks are set up for meetings four nights a week," said school spokesman Muir, who added, "I'm not looking forward to this fall one little bit." --Reporter Laurie Baum contributed to this article.