Your dd must be the same age as ds who just turned 4. Tomorrow he goes for assessment with the gifted specialist psychologist. i wish we had the options you have! Our options for fall are 3 days/week, half day pre-K that he's currently in (with a fab teacher who gets him), or all-day early public K (possibly in their new montessori program). I haven't spoken at length with our public school re: early k since i'm waiting to have some evidence in hand and also wanting to know if it's even recommended for ds. But the comments so far have been "we have lots of early readers in k, he shouldn't go early," so I think we may have a battle if that's what we choose. We're waiting on professional advice after ds's SBV to really make any decisions.
But if I were you, with your fabulous options, I would go for the all-day gifted school with sis if possible and if your dd won't freak about the all-day part.
There were some threads about parents wishing they had chosen for their kids to go to 1/2 day k and skip 1st grade at this age. That sounds like a good option too.
Good luck!
