Once you have selected the appropriate iCal calendar, assigned First and Last school days, set up the vacation periods, and added other dates for the school year, you are ready to send everything to iCal.
When you click the Done - Send to iCal button (near the bottom right of the Main Tab), ALL the dates you see previewed in the Text Field are written to the iCal calendar you have chosen as All Day Events. If you have also entered a location, every newly created Event will contain that information as well.
Clicking Done also clears out all of the dates set up in the Other Dates Tab, but any Event Titles that you created or edited will be retained for your next session.