Getting ready
They wake at 8:30 and the school door opens at 8:45. That is the whole problem, and it is a timing problem rather than a sleep one. They are already getting the right amount. It all just needs to move earlier, gently, starting now rather than the week before.
Right now they sleep about 11 hours at night plus a one to two hour nap, so roughly 12 to 13 hours across the day. The recommended range at their age is 11 to 14 hours including naps, so they are comfortably mid-band.
The target keeps exactly that and shifts it: bed 8:00pm, wake 7:00am, nap around 12:30 to 2:30. Same sleep, ninety minutes earlier.
Four weeks of roughly twenty minute steps gets there by August 30, which leaves the new rhythm locked in for a few days before the first morning. That matters more than it sounds. You do not want the schedule to be the second new thing on September 2.
Roughly twenty minutes a week. Small enough that most days it goes unnoticed, and slow enough that a bad night does not undo it. If a week goes badly, repeat it rather than skipping ahead. There is enough room in the calendar to lose a week and still land it.
They are enrolled full day, 8:45 to 2:45, so the nap happens at school. The aim between now and then is for the nap they take at home to sit where the school's will, so the body is already expecting it.
On a 7:00am wake, a 25 month old is usually ready around five to five and a half hours later. That puts the nap at roughly 12:30, running about an hour and a half to two hours.
Longer and the 8:00pm bedtime stops working. If they are still going at the two hour mark, wake them. This is the rule that protects the whole ladder.
They need roughly five to five and a half hours awake between the end of the nap and bedtime. A nap that runs to 3:30 pushes bedtime to 9:00 and undoes the week.
Sleep is the big one. These are the smaller pieces, worth adding one per week rather than all at once, so none of it feels like a campaign.
There is a spare week in the calendar. Repeating week two is free. Jumping to week three on top of a bad week is how the whole thing unravels.
Moving bedtime earlier often produces a few early wakes before it settles. It usually passes in three or four days. Hold the wake time through it rather than letting them catch up in the morning.
If only one part of this holds, make it the morning. A consistent wake time drags the rest into place on its own. A drifting one undoes everything downstream.