I certainly agree with those who don't consider this something for the Credit Union to take on.
I did go to a (secular) private high school. I was on scholarship. I had small classes, peers who shared my love of learning, received an excellent education, and it probably made a real difference in terms of getting admitted to an excellent university.
That was before the current movment to sabotage public education really started. At this point it seems that so much of the private school movment has ulterior political and religious motives. I can think of many much less controversial things for the credit union to do.
That is a very mistaken view. Not all private schools are for profit. Nor are they all highly funded. If they are non-profit then they will have ways to connect through their home and school associations as well as having a funding office if they are well organized.