In downtown Brooklyn, in an unassuming three-story concrete building on a very valuable piece of real estate at 141 Willoughby St., sits a New York treasure that most pass by without giving it much thought. For those who do stop, their lives can change forever.

That's what happened to Jessica Rueda. The Masbeth, Queens, resident was walking by it one day and saw the red flags and sign that read "Institute of Design and Construction" (IDC). Rueda walked in to ask for information and registered for the school a week later. Today, she's pursuing a career in the industry.

The little school, which is actually considered a giant in the local New York building trades, gives training in how to build houses and buildings. Its students go into contracting, building design and running construction sites.

Founded in 1947 by colorful New York architect and politician Vito P. Battista, who ran and lost races for mayor of New York seven times and once paraded a camel down the street to protest taxes, the school has become a prime source for education in the building side of real estate.

It costs $300 per credit, or $21,600 for a two-year degree, about 10 times less than New York University.

quot;I didn't exactly know what I wanted to do," says Rueda, who was 21 at the time. "I was in nursing school because I knew I could earn a good income, but it wasn't really me. I had no idea a school like this, where you could learn to manage construction sites or become an architect, existed. I've always loved to draw and work with my hands. It was perfect, and it I could afford it."

Going to class at night and working during the day, she learned to read blueprints, understand building code and design buildings on computers. Tough-talking teachers like Kathleen Avino, all of whom currently work in the construction business or as architects, made sure she did her work and understood the process.

"We live in a society of short-cutters right now," says Avino, a construction consultant who left architecture for construction management and has been teaching at the school for 20 years. "If you translate that to building, you're going to kill people. I make sure every one of my students understands what we teach them. We may not have multimillion-dollar facilities like NYU, but we offer a one-to-one education. If our students miss a class, I want to find out why. We take building very seriously and understand what it is to pass on the responsibility of working in this trade."

After taking time off because of a busy workload, Rueda realized how much she loved the construction industry and wanted to become an architect. She reenrolled and found her first job through the school. Now she works as a drafter for J. Sussman Inc., the oldest and best-known manufacturer of stained glass windows in the New York area. Founded in 1906, the Jamaica, Queens-based company did the windows for St. Patrick's Cathedral. Rueda's dream is to become an architect, and after getting her second degree from the school, she plans on applying to the Pratt Institute to pursue her career.

"My dream is to have my own firm one day," says Rueda, who grew up in Woodside to Dominican and Ecuadorian parents. "I can't thank my parents, teachers and boss enough. They believed in me. You feel that at the school. People care about you and what you're learning."

Thousands of New Yorkers wanting to work in the construction side of the real estate industry have passed through IDC. In addition to degrees in construction management and architecture, the city's top architects go to the school to take a course on passing their state licensing exam.

The great New York architect Philip Johnson, who built Manhattan's Seagram Building and AT&T Building, attended the school. In a speech, he once thanked founder Battista for helping him pass the test.

Today, the school is still a family business, run by Battista's son, Vincent, and granddaughter Elizabeth. With staff members such as Avino, who's taught there for more than 20 years, the school has a family atmosphere that fosters togetherness and support. Classes are small and instruction is hands-on. The school has a library where students who lack peace and quiet at home can come to study.     The atmosphere around the school is serious but friendly, with people hard at work. Of last year's graduating class of 16, 13 countries of origin were represented.

Vito Battista was an Italian immigrant who went to architecture school at MIT and worked on the 1939 World's Fair Site and Brooklyn Civic Center. A high-profile politician who was a New York state assemblyman, Battista started his own political party, the United Taxpayers Party, to help small landlords.

He believed in the craft of good building and in providing low-cost education to New Yorkers who needed it most. IDC combined those beliefs. The school started by training World War II veterans in construction management, something crucial during the postwar building boom.

"We still stand for exactly what my father wanted," says Vincent Battista. "Low-cost, high-quality education that gets people working in the field as quickly as possible. If they do their work and learn correctly, our students can be working in the industry within eight months. Every class we offer relates to the construction of buildings."

About 157 undergraduates attend the school and 60 to 80 will do graduate work. Some go on to get degrees at local colleges, others go to architecture school. Students can go to class during the day or at night. Most, like Rueda, work a day job, in the real estate, construction or architecture industry. They become drafters, assistant construction managers, building safety managers, estimators, specification writers, superintendents or expediters (who help architects prepare paperwork for city building and zoning guidelines).

"People don't realize how much paperwork needs to get done to build a building," says Battista. "We train them in all that. I personally try to get our students jobs. So do our teachers. You don't learn a trade here like mason work or electrical engineering, but you do learn how to supervise that work and make sure it works the way it should work. You learn how building structures work and how to maintain the New York building code, which is the strictest in the country."

Battista, like his father, doesn't hold back words. He thinks downtown Brooklyn is overbuilt and lacks the infrastructure to support the recent increase in residential buildings. He also thinks the New York building code is too complicated and changes too often. However, Battista says that New York is still the safest place in the country to be in a building,

"In New York, they understand the problem of high density and living on top of each other," he says. "Our code is the strictest because we take building seriously. You have to build safe with all these people around. We understand that at this school, and we teach it everyday. We have to."