The science bulletin board with its pictures of grasshoppers and leaves was pushed back. The bright red, yellow, green and blue triangles, squares and rectangles of the math corner were partially obscured.

Even Motek, the guinea pig, dozed only fitfully in his cage, seemingly aware that a more urgent mission had gripped the 23 boys and girls of Carmi Kobren's first-grade class at the Charles E. Smith Jewish Day School in Rockville.

Rosh Hashanah, the beginning of the jewish High Holy Days, would arrive at sundown Friday, and the 6-year-olds needed to prepare for it.

Almost from the first day of school they had been learning, through songs and games and projects, the Hebrew words for things associated with the holy days. From kindergarten through the 12th grade, the 850 youngsters at the school are taught in bilingual tracks, with 40 percent of their school day in Hebrew and 60 percent in English.

Early this week, Kobren's first-graders, one of four classes of beginners, had taken strips of paper and made holders for the wine cups that would grace their families' holiday tables. With crayons and Magic Markers, they decorated the holders with objects associated with Rosh Hashanah: the shofar that is blown to mark the period that concludes with Yom Kippur: the apples and honey traditionally eaten on Rosh Hashanah to ensure a "sweet year" ahead; and a set of scales.

"Why do we have scales?" Kobren asks the class in a review of earlier lesson. They are stumped. "Fish have scales...," one child offers tentatively. Kobran offers a warm smile of encouragement at the youngster's confusion over the pitfalls of English. "That's a different kind of scale," she explains, and switches her line of questioning.

"Who sits and looks at scales?" she prompts.

"God!" exclaims Ben. And suddenly it all comes back to them: how Rosh Hashanah, the beginning of the Jewish new year, is the time when God weighs our good deeds and our bad things, and how on Yom Kippur, 10 days later, we can start the new year with a clean slate.

The project for Wednesday, said Kobren, was "the first hard thing I'm going to ask you to do." The objective: to construct a new year's greeting card in the shape of a dove, with multicolored accordion-pleated wings and a stiff paper platform to stand it on.

What made it really hard was that the children, whose English writing skills do not go much beyond a cramped printing of their first names, were going to print the new year's greeting, Shanah Tovak, in Hebrew, on folded paper that rode astride the dove.

Kobren, in her fourth year of teaching at Jewish Day School moved brisky about the room, offering help, turning mishaps and problems into opportunities for learning. "I don't have any scissors," complained one child. "Oh, I'll give you a pair if you tell me what the word is in Hebrew," responded Kobren.

She was full of praise for accomplishments. "I made my first shin!" exclaimed Daniel, proudly exhibiting the wobbly Hebrew letter he had copied from the blackboard. "Look, everyone," Kobren exulted, holding up the child's paper. "Daniel made his first shin. You'll be making a lot of shin this year, Daniel."

In her crisp white blouse and denim skirt, Kobren maintained unquestioned control of the bright, sunlit classroom, brusquely rejecting suggestions by reluctant scholars that they might like to go home. Her enjoyment in the accomplishments of her charges and her delight in their unexpected responses shone in her eyes and her ready smile.

She took pains to make sure that each child's dove--some of which, to tell the truth, ended up looking more like fat chickens--really did stand up. When Jona, more sophisticated in the uses of greeting cards than the lesson-plan anticipated, asked, "Should I write a note to my mom" on the card, the teacher laughed appreciatively, gave him a fond pat on the cheek and explained gently, "Well, you don't know how to write anything yet."

Before the year is out, explained Geraldine Nussbaum, assistant prinicipal of the elementary school, Jona and his classmates will be reading and writing in both English and Hebrew.

Kobren, who lived in Israel and went to school there for seven years, teaches, in addition to the Hebrew langauge, the essentials of Judaism but avoids the theological distinctions that separate Orthodox, Conservative and Reform branches of Judaism. "It's a community school," she explained. "We have children who walk to synagogue" as the Orthodox do "and children who ride to synagogue. We have children who don't kiip Kosher at home...but here we are all equal."

Although the holy days the children were preparing for are solemn, preparation for them brings its own excitement into the school, explained Dr. Shulamith Elster, headmaster. "It's always a good way to start the school year," she explained. "You have school for seven days or so, then you have two days off. Then another week, and another two days off" for Yom Kippur.

"The only sad note around here is that this year the holiday comes on a weekend," she laughed.