Many school districts have a week long spring break or winter break and vacations from school should be planned then. In high school a lot of learning happens in a week and while you can make up the tests and assignments, you cannot replace the learning that happens during oral instructions and class discussions. With the flu going around many kids are already missing a week of school just for that and it cannot be helped. I'm all for planning vacations around the school calendar, except in the case of the lower grades such as kindergarten and first grade where you really will not miss and have to make up as much work.