Its City League title already assured, Heights didn't flinch when South pulled to within four points with 2:46 to play Thursday night.
The host Falcons (18-2, 15-1) went to 6-foot-8 sophomore Perry Ellis for a layup and allowed the Titans just two points the rest of the way in a 59-50 victory.
Heights coach Joe Auer said his club just stayed the course.
"A win is a win," Auer said. "We were confident in our ability to win tonight, but it was a close game.
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"Now, we're 0-0 and back to single-elimination basketball. We're real proud of a tremendous season.
"If you're not going to take time and smell the roses when you're 18-2 and 15-1 in our league, then you're a fool."
When the teams met Jan. 26 at South, Heights rolled to a 72-23 victory. Thursday, South had matched that point by halftime, when Heights led, 30-23.
But the Falcons' steady second-half play denied South any hope of an upset.
Ellis finished with a game-high 21 points, often taking it up against South's 6-5 Tony Buchanan.
"I thought his energy level was pretty high and I thought he did a great job," Auer said of Ellis. "He has the ability to score the basketball a lot of different ways. But that's what we expect him to do night in and night out."
Buchanan was able to give almost as good as he got, working inside and hitting short jumpers for 13 points.
"I feel like we've got a lot that we can work on to get better at, but I feel that our effort has been good except for Tuesday night (a 69-22 loss to Kapaun Mount Carmel)," South coach Steve Lilly said. "(Heights) has got a lot of the pieces of the puzzle, and it's just hard to keep it contained the entire game."
South (2-18, 1-15) 8 15 17 10 — 50 Heights (18-2, 15-1) 13 17 15 14 — 59
SOUTH: Perkins 6 0-0 14, Keiswetter 3 0-0 7. Glenn 2 0-0 5, Bradley 5 0-0 11, Buchanan 5 3-4 13. Totals 21 (5) 3-4 50.
HEIGHTS: Dobbins 2 2-2 6, Wessel 7 2-4 16, Moore 4 0-0 10, Ellis 8 5-8 21, Riley 3 0-0 6. Totals 24 (2) 9-14 59.