We have aspirations for our kids that includes sending them to the 'best' available school.
I totally understand making huge efforts and taking sacrifices on the nose to give your kid a fighting chance in education.
But you need to pay at least as much attention to "available" as you you do to "best".
As in look at what is realistically available to you, and then pick the best from that. Not choose the best, and try and make it available to you if realistically it isn't.
If your daughter has to move, better it is at the end of Y9 than at some point in Y10/11 due to say a change in circumstances that you have no control over. Like job loss. Marriage breakdown. Husband snapping and refusing to carry on building up a debt to satisfy aspirations he doesn't appear to believe the family can afford.
So I would say in terms of "available" your choices need to be based on realistic assessment of potential changes. Not just the best case scenario of everything staying as it is today.
Probably the best available education for your children is one that is sustainable for all of them, and leaves the family far far freer of economic and time pressures that have the potential to suck the stability, security and ability to live in contentment .. right out of it.
And both of you need to be one the same page in creating the solution that provides that. A solution based on both ups and downs being a reality of life, so that it is robust enough to withstand the stormier times, and won't leave you two and your children in this place again. Becuase screwing up once is human. Twice... and it starts to look a tad like a habit of making a priority of your wants (champagne taste for best education/activities) over your children's needs (sustainable, good enough education and a relatively content, secure, not overly stressed home life).
As horrible as this must feel, and I do sympathise, there is good news. This comes under the heading of one of life's resolvable problems. It must feel all shocking and scary and emotional rollercoastery. But in the grand scheme of things you have lots of options due to your income and assets, and you all stand a very good chance of coming out of the wash relatively unscathed. Just as long as sustainability is built into the solution.