The bell rings at 8:30 whether you're ready or not. Between waking kids, making breakfast, finding the other shoe, and actually driving there, the margin for error is about zero. A backward plan turns that margin into a sequence you can follow.
School mornings don't fail because of one thing. They fail because five things happen in sequence and one of them runs long. The kid who can't find socks. The cereal that gets spilled. The backpack that's still at the bottom of the stairs. You can't prevent all of that, but you can budget time for it.
Ready Time works backward from the school bell. You add each step with honest durations. Not the best-case scenario. The real one. If getting dressed takes 15 minutes including the sock negotiation, say 15 minutes. The plan tells you when to wake them up so you arrive with time to spare, not time to panic.
More routines