An important item to remember to purchase in advance if you have children is extra home schooling supplies. You may remember trigonometry, but could you teach it to your children without any materials? If you self-quarantine your family because of a flu pandemic it will be nearly impossible to acquire books or other supplies. Post-TEOTWAWKI, after your generation is gone, advanced math and science will be rare and valuable skills.
From #1 Son: Stocking up on Home Schooling Curricula
