Absenteeism: At what point do you involve administration if a child has been frequently absent?

There are a couple of parts to this. I have worked in schools where I have been asked by admin to let them know when students have missed more than 2 days in a row. Usually after the first day, I will reach out, just saying that I missed the student and hope everything is okay. I will offer assistance if they need it. Usually parents will get back to me quickly if it's just a minor illness or a family emergency. I would say anything past 3 days in a row should go to admin, especially if you haven't heard from the family once you've reached out. I would also say that if it gets to a point that it is impacting their grades or their performance in your class, that it's time to sit down with admin and discuss next steps. They may need to be put on an attendance plan.