Herndon (22-2), ranked No. 13 by The Washington Post, broke the 100-point barrier with a 106-52 win over Patriot. Patriot (4-20), of Prince William County, had won just one game all season before winning three straight to take its conference title.
South Lakes girls, (23-3), ranked No. 12 by the Post, were led by senior Abigail Rendle with 18 points in a 71-43 victory over Lake Braddock.
South Lakes boys (18-8), which has lost only one game since late January, continued its run with a 64-48 victory over West Potomac. Brandon Kamga scored 28 points for the Seahawks.
Regional action continues Tuesday. South Lakes girls host Centreville at 5:45 p.m., followed by the boys against Robinson at 7:30 p.m. Herndon hosts Hayfield at 7:30 p.m.
The Region semifinals and finals are Thursday and Friday at Robinson High School.