Having seen this video of a previous bird-shooting at Herlufsholm, I don't think parents are present, at least not the whole day.
It appears to be a merry and wet... event.
But I understand that former students can visit and watch a procession early in the day.
Thanks Muhler: the 'wet' intrigues me...do you know what they are drinking? It doesn't look like beer (I can't imagine beer at a high school but this is perhaps Danish tolerance?)