Changing attitudes about single parenthood have opened new doors to school-aged children, who often have a difficult time finding permanent homes.

While many couples still look to adoption agencies for small babies, more and more single men and women are looking for youngsters between ages 5 and 15.

At a recent meeting for prospective parents at the Pierce-Warwick Adoption Service in Washington, three of the group of 11 were single women. Carol Siemens, who runs the adoption division of the Prince George's County social services department, said that of 100 prospective adopting parents studied in the last six months, 10 were single persons.

Siemens said that in the past five years, social workers have come to realize that marriage is not necessarily a prerequisite for being a good parent.

Gerald Rogers is an example of the new trend. At the tender age of 25, Rogers, an Army sergeant, will officially become the father of 11-year-old T. J. (Anthony Jerry Christopher Rogers) at the end of the month. T. J. has been living with Rogers for a year now and Rogers says he is so pleased with the relationship that he is now trying to adopt a second boy in Prince George's County.

Rogers, who lives in Columbia, is an alcoholism counselor at the Bethesda Naval Center. A former police department employe in Texas and currently a Boy Scout leader, Rogers feels he has a great deal of experience working with troubled youngsters. After seeing a television ad about adoption, he said, he decided, "I had a place for a child of my own."

Rogers, who grew up in Ohio, said he is particularly aware of the importance of having a father. "I wished that I had had a consistent adult male when I was growing up."

T. J. came to Rogers through Pierce-Warwick, which specializes in finding homes for children with problems. According to Rogers, T. J. had been a ward of Baltimore County since he was 3, had been abused by his foster parents and had spent the last few years in orphanage.

T. J. is a slow learner and sometimes has a hard time behaving in school, but he has made considerable progress in the past year, Rogers said. "My feeling is that he wasn't able to get the attention he needed (before), I don't push him. . . . I try to keep his time well structured."

Rogers is also a computer enthusiast, and now uses his home computer to teach T. J. math, play games and entertain babysitters.

"My whole life style has changed," Rogers said. He no longer leads a bachelor's life, but he wasn't given up dating.

When Rogers began looking for a child to adopt about 18 months ago, he ran into some skepticism from social workers because he was so young. The soft-spoken new father said he was asked whether he were a homosexual, but the question didn't bother him because he has expected it. He said his friends and family have been supportive of his decision to adopt.

Marriage? Yes, Rogers said, he would like to get married one day, but he's "very cautious." He admitted that finding a woman willing to take on a ready-made family of adolescent boys may not be easy.

T. J. seems happy with his new life. He decided several months ago to add Jerry to his name and likes the idea of the Rogers family being called Big Jerry and Little Jerry. He also said he's learning all sorts of new things. He spent last week at Boy Scout camp, where he learned about first aid. "You have to suck the poison out of a snake bite, but you can't swallow it," he explained with a broad smile.

Most of all, T. J. loves painting pictures and his father's fried chicken. He is equally excited about moving to Stuttgart when his father is transferred to West Germany in the fall.

And the sergeant is hoping he will have a second son to take along.