As the owner of an older girl with ADD I'll make a couple of general points based on our experience, if that helps?
Yes, absolutely you MUST tell prospective schools, and supply them will all the relevant documentation. Full disclosure is vital - the best school for your child is the one that wants to teach her. There's no point getting her into an academically-sought-after school that isn't prepared to go the extra mile for her and might even seek to manage her out if problems arise. If you've knowingly withheld information that the school might reasonably need, then you are being unfair to the school and to your child, and will put yourself in a very difficult position if problems arise or your child needs support.
Out of all the families I know with quirky but bright kids (and it's a lot, you do tend to gravitate towards people who share some part of your experience) the ones who have had a good outcome have been where parents have prioritised the child's emotional and social wellbeing in choosing schools. All of these children have reached their academic potential in schools that were not hothouses. The ones I know that have had really bad outcomes (including things like school refusal, eating disorders, child being excluded or asked to leave, serious MH problems) have been where people have (correctly) spotted their child's high academic ability, but have prioritised meeting their academic needs over their social and emotional ones. Some of those kids have crashed and burned really badly.
Super-high-achieving schools get that way because they select pupils who are straightforward super-high-achievers. They do not need to bother themselves with children who find some aspects of school life difficult - some will make the effort do support square peg children anyway, but many will not, or will pay lip service but not really deliver. You really really want to know beforehand what the school's reaction will be if things don't go to plan in some way, whether academically, or socially and emotionally. Some of the really bad outcomes I referred to above have involved high-profile premier league academic schools, and children with stand-out ability IQ scores - a high-quality brand name is no guarantee that it will suit your child. It is really buyer beware, and you can only assess the school's attitide if you give them all the information beforehand.
We are in the state system rather than private, but the principle is the same - find a school that wants to teach your child, rather than trying to get your child into the most prestigious school. For primary we chose a school that is considered quite rough over the league-table topping middle-class primary, and they have supported her fabulously. For secondary we have gone for a socially-mixed comprehensive over the North London superselective options, and again, early indicators are good.
I'll say it again: the best school for your child is the one that most wants to teach her. League-tables and prestigious school/uni destinations are no indicator of whether the school wants to work with your child.