First my school district has a great vacation policy. I would check with your school.
Second, I have to say BS to all the people who do not have the faith and confidence in their children to think they could not take a vacation during the school year and make it up. My 6th and 10th grader both just missed 7 days of school. They both have all A's. The 6th grader is in 7th grade Math, Science, Social Studies, Language Arts, Band and 21st century skills (last two are electives). My 10th grader is in Biology, Spanish 2, Geometry, History, and Life Fitness. They have block classes that are trimester's so they switch classes each Tri. My 10th grader took her exams early (the week we left) and came back a week after her new classes started.
Third, in the real world you have to learn to be able to take a vacation and come back to work and start back up or make up the work you missed. It is a very good lesson in responsibility.
To answer your question, if the school allows it they usually have forms to fill out so just fill out the forms and have your students talk to the teachers. The forms we had needed the teacher signature and then the parents. It all works out OK.