Why Fridays???

My daughter is about 8 weeks into her first year of preschool. She only goes 3 days a week for 3 hours a day, so that's a total of 9 hours a week, and YET, we're going on our third illness. And, they ALWAYS start on Friday. And the last two have been the Friday before someone's birthday party on Saturday. She's been invited to three parties and is about to miss her second one out of the three. I'm seriously considering homeschooling next year because I can't take this stress! Luckily, this one doesn't seem too bad (knock on processed particleboard), so there's still a chance she might get to attend the party after all, and, at the very least, she might not miss another day of school. I just hate when she's under the weather.