I count 22 rows at Jamieson. Anyone who wants to look for themselves can see the picture I used here:
https://carolinapreps.smugmug.com/StadiumProject/Grimsley/i-s9wRwtX/A
You can zoom in on the picture to make it easier to count.
It looks like there are 30 rows at Simeon, but only four "complete" sections (three that are the same size and two that appear to be about half the size of the others, one on either end). Jamieson has 8 sections (7 full and 2 halves) on both sides, while East Burke has 27 rows with 5 complete on one side and 7 on the other (4 and 2 and 6 and 2 as defined before). At East Burke there is also room to sit or stand on the top above the stands as there is no wall up behind the seating area as at Simeon and Jamieson.
But the only objective estimate I know of is what Chris compiled on his travels. He lists an estimated capacity for each on the "team pages" for the schools on his website. Here's what he has for each school listed:
East Burke 15,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/244
Simeon (High Point Central and Andrews) 15,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/196
Jamieson (Grimsley) 14,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/258
A,L Brown 12,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/181
McDowell 13,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/243
For what it's worth he also has Asheville at 12,000
https://carolinapreps.com/teams/teams/frontend/teampage/teamDetails/158
I happen to think that Asheville has the "nicest" stadium in the state due to the setting, with Asheville High School being a beautiful place with architecture that more modern schools can't match, but that's just personal opinion.
Chris might be off on these estimates, but he's probably seen the most venues of anyone around and he stated on a thread once (gone now that the old Carolina Preps boards have vanished) that his opinion was that East Burke was the largest.