Realistically, you’re wrong. In my bog standard , one form primary, we have at least 7 kids that will never be able to live independently or even learn to tie their shoelaces(never mind be able to read, write , do maths to an even bare minimum level), 5 more that could possibly have some independence, but working ability would definitely be questionable. 15 more that are on the cusp, there is potential there , but even if they do make , we are talking minimum wage jobs(and thus propped up by benefits anyway). That’s without all the kids that left for specialist provision. The number gets significantly higher , and again, they can be in either group.
You might want to think that the numbers are small to suit your narrative, but they aren’t.