Gaithersburg seventh graders have a Christmas tradition of gingerbread and geometry that is all their own, thanks to a tireless teacher who has become known far and wide in Montgomery County as the Gingerbread Lady.

Since 1976, Marilyn Hembrock, a seventh-grade math instructor at Ridgeview Junior High, has devoted two or three classes each December to gingerbread houses.

Her students may build triangle houses with pentagonal windows, hexagonal houses with round windows, plain old rectangular houses with plain old square windows -- any combination of geometric shapes that forms a house.

"The pieces don't always fit together, but the class always seems to work," said Hembrock.

Shannon Tordella, 13, of Germantown, spreading icing around green windows shaped like shamrocks, appeared to sum up student sentiment: "This is one class I don't mind staying after for."

"I love to decorate things," said Marion von Doenhoff, a 12-year-old from Germantown, as she positioned a candy Santa in a gingerbread chimney during a pre-Christmas class. "I decorate all the birthday cakes for my brothers and sisters."

John Hoppes' house -- he called it a Swiss chalet -- has diamond-shaped windows. John, 14, of Darnestown, completed seventh-grade math last year but returned to the class this month for the gingerbread sessions. As he carried his decorated house from school last year, he tripped on the curb and smashed it on the pavement. "it wasn't all bad, though," John said. "I just had to eat a lot of gingerbread."

Hembrock invests about $100 in candy at the beginning of the Christmas season so that her pupils can have a good selection of decorating materials.

Her reputation as the Gingerbread Lady extends far beyond Ridgeview. She estimates she has taught gingerbread house-building to about 120 teachers, neighbors and cake-decorating enthusiasts. She thinks she has built as many as 250 houses since she made her first one 12 years ago.

Hembrock includes a bit of German culture in each of her gingerbread geometry classes and expands on the topic when teaching gingerbread construction for one day each December to Marie Ferrington's German students at Ridgeview.

"We talk about Hansel and Gretel and also about the German custom of having a 'Lebkuckenhas' around the house for the holidays," Ferrington said. "My students really look forward to it."

Hembrock said she has never made two identical gingerbread houses. Or churches. Or barns. Or dog houses. Or wishing wells.

But at least one of each of those structures -- a dozen in all -- was part of the architectural plan in the 4-by-6-foot gingerbread village she engineed three Christmases ago for residents of the National Lutheran Home where her husband Richard works as a chaplain.

Residents of the home, which moved from Washington to Rockville last August, spend many hours looking at the cakes Hembrock bakes for monthly birthday parties. Enthusiasm is highest just before Christmas when everyone tries to guess what kind of cake the Gingerbread Lady will bring this year, said nurse Mary Ann Haley.

A year after Hembrock made the village, she was determined to come up with an even more elaborate gingerbread gift. She built a 30-inch high replica of the chapel at the Lutheran home and covered the roof with nine pounds of nonpareils.

But the real artistry was visible through the front doors. Pews, an alter, a pulpit, electric chandeliers and an organ -- "The organ tasted good, too," said Hembrock's 11-year-old son, Joel. "I ate it."

Hembrock's recipe, which she freely shares, is the product of considerable trial-and-error. She began experiments in the kitchen 20 years ago in Texas as a teen-age 4-H Club member.

She attempted her first gingerbread house when she and her husband, then an Army chaplain, were stationed in West Germany. She admired the houses in bakery windows and set out to make one for her daughter Sarah's first Christmas.

"The very first one I made was awful," Hembrock says. "It was from a recipe I cut out of a Stars and Stripes newspaper. After two days, it fell apart."

Dough that students rolled out during their geometry lesson this year contained flour, sugar, eggs and shortening as well as molasses, ginger and nutmeg. Icing consists of egg whites, powdered sugar, lemon juice and cream of tartar.

Basic ingredients for one house cost about $3, although costs usually rise to $10 because of the nightlight Hembrock puts inside and the assortment of colorful candy used for extra decorations.

In addition to the gumdrops, red hots and candy canes, Hembrock's houses have strawberry licorice shutters, marzipan furniture and stained glass windows made from life savers that melt when the cake is baked.

Margie Bittenger, owner of the Little Bitts Shop in Wheaton, which sometimes displays and sells commercial gingerbread houses, says Hembrock's creations" really stand out" because of the stained-glass windows. Hembrock does "excellent, excellent work," Bittenger said.

Hembrock, who also makes nativity scenes and tree ornaments out of gingerbread, says she isn't interested in making houses to sell.

She spends about six hours on a typical house and estimates she would have to charge $50 or more.

But the Gingerbread Lady is not totally opposed to praise and profit. In 1979 she entered a house in the Montgomery County Fair and was named grand champion of the cake-decorating competition.

She walked away with a purple ribbon and the loot -- $5.50.