There is nothing unusual about Bladensburg High School winning the Prince George's County Class AA basketball crown.Since the 56th Avenue and Tilden Road school opened in 1952, the Mustangs have captured at least a share of the county title a dozen times and have advanced to the state playoffs six times, twice emerging with the Maryland championship.

A new era has begun, however, with first-year coach Ernie Welch guiding the fourth-ranked Mustangs to a mid-March visit to Cole Field House, the traditional site of the state tournament.

Welch, who is preparing his squad for tomorrow's 9 p.m. semifinal battle with Woodlawn of Baltimore, attributes the Mustangs' highly successful, 22-1 campaign to "a sense of purpose from day one . . . (while) other people postponed their purpose."

Welch, a 1961 graduate of Bladensburg who took over from Roy Henderson after 12 years as his assistant, said many county teams took the regular season lightly, trying to produce their peak performance for the end of the season and the playoffs.

"I think one of the big things we did [WORD ILLEGIBLE] the rest of the teams around the county didn't do is we didn't spend the whole season getting ready for the playoffs," he said. "One of the things I asked them to do, one of the things they do very well is . . . 'TCB,' take care of business, and we did this very well; whether the team (the opponent) was 1-12 or whatever, we went out and did it.

"That clarity of purpose is why we dominated the league. You have to be clear as to your goal. It takes a lot of dedication to work hard for three months," Welch added.

The Mustangs finished with a 9-1 league record, three games better than Potomac of Oxon Hill and six games better than third-place DuVal of Lanham. Bladensburg defeated Potomac (20-5) for the third time this year, winning the county title Saturday by a score of 85-83.

The only blemish on the Mustangs' record was an 87-79 mid-season setback to DuVal.

"We stayed together. A lot of other teams had troubles during the season, but we stayed together," said senior Skip Speaks, a 6-foot-4 1/2 forward who led his team with a 23.1-points-per-game scoring average. "We just wanted to win that much. We believed in everyday competition. We take every game as a challenge."

The Mustangs featured an explosive, fast-breaking offense, which averaged 87.2 points per game, and a gambling defense, which allowed 66.9 points per contest for an average victory margin of more than 20 points per outing.

Joining Speaks, a three-year veteran and certain all-Metropolitan first team choice, in the starting lineup, which remained intact for all 23 games, were 6-foot-2 guard Levi Morton, the leading career offensive rebounder in the history of the school with 306, who averaged 19.8 points and 10.8 rebounds; Bryant Thornwell, a 6-4 senior forward; Thurl Bailey, a 6-9 1/2 and still growing junior center whose size 17 sneakers left the floor often enough to grab 11.5 rebounds a game, and point guard Willie Swearinger, a 5-9 junior playmaker. Welch regularly used nine men, with 6-2 forward Charles Butler and 5-11 guard Paul Bullock the first off the bench.

Welch credited much of his success to inheriting a veteran team, which had gained much experience during two "medium years" since Bladensburg took its last state championship in 1975.He also said the team members' temperament, level-headedness and willingness to put in the necessary practice time helped the Mustangs advance so easily through their season.

"It probably should be said - and a lot of teachers who have been around the school for years have agreed - this might be the nicest bunch of kids we've ever had here," Welch said. "They walk down the hall and say hello. They're not a bunch of jocks, they're not surly, they're not on ego trips."

The players who played on the 11-9 team of 1975-76 and last season's 12-11 squad are anxious to play in the state competition for the first time.

"Yeah, I can't wait - that's what everybody's waiting for," said Speaks of his team's trip to Cole. "I think we'll play even better. Some of us have been around three years and we really want it (the state title).This is further than we've ever been before. That would be just what everybody wanted."