For the past six years, the Tilbury Woods section of west Columbia has been a model neighborhood, a complex of inexpensive apartments where young families and singles settled and children frolicked in a giant "tot lot" beneath ancient cedar trees.

Tenants at the 14-year-old Tilbury Woods, among the oldest apartments in this 16-year-old "new town," said they were especially proud of their friendships with 20 handicapped workers who policed the grounds for trash, swept walks and emptied dumpsters.

But that idyllic picture changed this month, when the owners of the 300 apartments sold them to the Krupp Co., a Boston-based real-estate developer. The decision by Krupp officials not to renew a $40,000 contract with the handicapped porters and their plan to convert the Tilbury Woods to an adults-only facility has caused an uproar among tenants and Howard County officials.

Despite assurances to the contrary, some tenants say they fear their leases will not be renewed because they have children.

"It's really a crime what they did to the porters," said Shauneen Hicks, a mother of two who has lived at Tilbury Woods for six years. "They were very much a part of this neighborhood.

"The sad thing is that they will be affected immediately," said Hicks, who operates a small day-care program in her home. "The effects of going all-adult won't be felt for years."

Local Krupp representatives declined comment on either the no-children rule, which will apply only to new tenants, or the contract with the 20 porters from the Howard County Association of Retarded Citizens. Instead, the officials referred all inquiries to Krupp vice president Jack Davenport, who said some residents had "overreacted in a lot of cases" to the changes.

"It all smacks of being very exclusive, very discriminatory," said John T. Everett, executive director of the association of retarded citizens. Krupp's decision against renewing its annual contract with the private, nonprofit agency "is not at all in concert with the Columbia concept," Everett added.

"The whole idea behind this city was that it be all-inclusive, a place where all people could live and work," Everett said. "Columbia was supposed to be for everybody: whites, blacks, Hispanics, homosexuals, whoever. There's something much deeper here than just a cutback."

Everett said the porters, all of whom are mentally retarded, have been reassigned to other projects around the county.

Tilbury Woods residents, meanwhile, said the new owners are not tending the grounds and buildings as well as the porters did. "This is not a high-class place," said one parent, who asked not to identified, "but several of us have noticed a change for the worse in the past couple of weeks."

Frequently, trash has been allowed to accumulate on front lawns and around dumpsters, said the woman. The mother of an 8-year-old boy she said she was "shocked" by the announcement that future available units would be for adults only.

With one-bedroom units renting for $321 a month and two-bedroom apartments for $361, the Tilbury Woods housing was some of the least expensive in Columbia. The subdivision already is showing its age--paint is peeling in large patches from some exterior walls--but it also has attracted a mix of young professional couples, single parents and blue-collar workers.

Krupp acquired it and four neighboring developments from a Canadian corporation, but thus far, has designated only Tilbury as the site for all-adult housing.

Some Tilbury Woods residents said they were pleased by the decision. "I was happy to see it happen," said Phil Peters, 42, who has lived there for four years. "There have been problems with some of the kids--rowdiness and the like."

Peters, who teaches French and Latin at nearby Atholton High School, said he was planning to move to a larger apartment but may not if the development is all-adult in a few years.

Tilbury Woods has 20 families who receive federal rent subsidies under a program run by the county Housing and Community Development office. An office spokesman said he was uncertain whether Krupp would allow those subsidies.

"There has not been a great deal of communication between Krupp and us," said David Zappasodi, who runs the county's rent subsidy program. But he added, "We are operating on the assumption that they will continue to voluntarily accept those units."