That's a 29-person group if my headcount is correct. Your head spacing is not too bad, not great, but not too bad really. I think the biggest issue is that the focal length looks a little too short, which causes the head sizes to be a bit smaller on the girls who are only a few feet farther away...it would look better with a longer lens, shot from much farther away.
But the real issue is that they are packing in there like sardines in a tin...the posing area is VERY small, very cramped, for 29 people. What's causing a bit of a problem is the guy with the baseball cap, sitting there on his jacket, and with his legs overlapping the gal to his left...HE is causing the entire left hand side to fracture off.
This would be a tough location, but I would probably have let the group go wider, and looser. You have EIGHT men on the left, and close, then 21 other people all crammed in to about the same width...there's just a massive log-jam of people from the center to the right...I count 18 heads in an area as wide as the eight guys on the left take up.
The three guys in the front are also taking up a LOT of prime real estate by being square-shouldered, and the reddish jacket in the lower left corner on the step...THAT spot could have had somebody seated.
I might have had five people KNEELING, in the front row, made the second row all angled to the right, but heads looking ahead, put a guy on the step lower left, had a guy stand to the far, far left of that step, and in that way, give 10 people in the back cluster much more presence.
Anyway...this kind of a shot is something that not many people do. But the issue really is not enough space, and a few posing decisions, like the THREE guys in the front that KILLS the shot. Having just three men in the front ruins the shot, basically... it forces your hand. You need to ANGLE the bodies to get more people in a small space; Everybody is broad-shouldered, which is very "static and dull" and even worse, makes the 29 people appear (well, not just appear, the ARE) more-crowded into too small a space. I used to work at a portrait studio, and had to shoot 15, to 25-person groups three to five times a week. It's kind of a pain in the butt. But there are "methods", and the biggest one is getting some body angle for tighter spacing/more efficient use of the actual space available.