The wisdom of a mother can sometimes prove fruitful for her offspring. Just ask William Lindsey.

Six years ago, Lindsey's mother gave him an ultimatum: get involved in some sport or activity, or she would do it for him. At the time, he had two choices: day camp or tennis. He chose the latter.

"I selected tennis because I thought day camp was for sissies or something," Lindsey recalls. It might well be the best decision he will ever make.

What began as coercion turned out to be a natural. In fact, Lindsey became so good at the game that first year, as a 12-year-old, he joined the National Junior Tennis League and qualified for the national championships.

Since those first eventful days as an advanced beginner, Lindsey has played in more than 30 tournaments on the east Coast and in the South, making the finals nine times. He has also joined the American Tennis Association (ATA), a predominantly black group.

During the school year, he plays for Ballou High School. In three years he has compiled a 36-4 in singles play in the Interhigh, and is undefeated this year.

Proficiency in any individual sport demands proper training and coaching. Lindsey has had the best.

"In 1977, I went down to Texas Southern (University in Houston) with the ATA," he said. "It was there that I met Arthur Ashe. I was very impressed with him as a person.He helped me a lot with my serve."

But the man who Lindsey says really nurtured his development is Ashe's teacher, Robert Johnson. Johnson has been instrumental in the development of several outstanding players, and his is one of the most respected names in the world of tennis.

Lindsey is a definite admirer. "He has spent a lot of time working with me," he says. "I have traveled a lot with him and learned a great deal. He is a tremendous teacher."

If Ashe and Johnson provided the pointers, Ballou coach Lamar Pearson instilled the self-assurance. Pearson has coached tennis at the Southeast school for six years. His teams have won three Interhigh titles and finished runners-up three times.

Lindsey is equally full of praise for him:

"Coach Pearson has really helped me with my confidence. Sometimes I have a tendency to play down to the level of my opponent. That's where he has really helped me, by telling me to be more aggressive."

Pearson sees tennis as an avenue to a college education for athletes from the public schools. Some of his former players, Joseph Ragland (Southern University), his brother Michael Ragland (St. Augustine College), Tyrone Holland (Johnson C. Smith), his brother Dennis (Southern) and Charlie Ryder (Southern) all earned athletic scholarships, and all currently compete on the national circuit.

Interhigh coaches are not paid to coach tennis -- they volunteer. Yet the interest and numbers in tennis have increased appreciably in recent years despite the school system's benign neglect. Once Ballou, Wilson and McKinley were the only schools with respectable programs in tennis. Coolidge, Roosevelt and H.D. Woodson have now joined the pack.

"Television exposure has had something to do with it," Pearson said. "But I think the access of summer tennis camps and programs has done a lot, along with the fact that some of our people have received scholarships.

"This year alone we had 40 people to come out. In the past we would have been lucky to have 10."

Lindsey's summer tennis activities have enhanced his game. He is a tennis instructor for the National Junior Tennis League summer program and for the National Youth Sports Program at the University of the District of Columbia.

During the school year, he also played soccer for three years at Ballou, and as captain of the team, led them to an Interhigh second place in 1978, the championship last year and the quarterfinals this season.

Off the field and court, Lindsey is editor of the Charter, the school newspaper, and recently was cited by The Washington Star for his outstanding contribution to the paper.

Meanwhile, he is trying to move up on the junior tennis circuit. He is ranked No. 41 by the Middle Atlantic Tennis Association. He will have an opportunity when he travels to Duke University June 9-15 to compete against 300 of the top junior players in the country.

"This will be a golden opportunity for me to get more exposure and elevate my game," the 18-year-old says. "Then I can hopefully qualify for the national circuit."

He is not the only tennis player in the family. His mother Ethel and father William play occasionally, and his sister Karen, 7, is taking lessons. His 12-year-old brother Darryl has been ranked as the top 10-year-old in the area.

A sister, Darlene, is a dancer at the Duke Ellington School of the Arts.

Lindsey says he plans to attend North Greenville Community College, a two-year school in Greenville, S.C., and go on to Clemson University.

Not surprisingly, his mother is top-seeded with him.