If you have a highschooler, odds are you already KNOW the teachers and their policies. And, you probably do know the demands of your child's courses.
Schools do vary widely, and I am assuming your kids are in public school. I would talk to each individual teacher, and see how your child is doing, how they feel about the amount of work that will be needed to make up, and their policy. They may think it's a good opportunity for your to have a family vacation, or they make think it's too much time missed in the classroom (not being sick, which can't be helped). Teachers have widely differing views on these things. So do schools.
My kids are in private school, but my 7th grader son has ADHD, so for him to keep up with his demands at school is very hard. Plus, they are both in a high math class. Although my DD could make up work easily (she missed 11 days first trimester due to H1N1 and strep) my DS has a hard time. I couldn't pull him out for an extra day. He'd get dug down into a deep hole.
I do think open communication is important! Start talking with them before you book. Or, if your child doesn't want to miss, and you are planning the trip, I did this. I stayed with my best girlfriend at her house for a week, while my folks went to Florida. It was actually fun - and her mom was so nice, she even packed me lunch every day. So maybe that is an option, if the schoolwork is too much to miss..
Good luck with this!