Assuming a 180 day school year (which would actually mean a 10 day period would be closer to 3-4% not 4-5%), that means that half of the year they are not in school anyway. So they have a good chance of catching it outside of school days anyway even if they catch it annually. Besides that, if that's that's a huge and consistent problem, school could just reduce the number of holidays by a week or so. The variance of number of school days throughout the world is already larger than that.
The weekends do count, out of the 10 days they'd be out, up to 4 would be weekend days. So, really they'd have missed around 6 or 7 days of actual school. But it could also happen to fall in a public holiday, which will reduce the number of days even more. And there are school breaks throughout the year.
I find it hard to believe that many people are living such in the edge that, if their kid has to miss a week or so of school in a year their finance and jobs fully crumble.
There's 104 non school days regardless of any other days without school. It only takes 76 other days off (June 15-august 15 + 3 additional weeks off) is youe 180 days off.
