In the entire United States, there are only about fifty Orthodox Christian schools for all or part of kindergarten through 12th grade (K-8 and high school). A few years ago, I did a research project to try to identify all the Orthodox schools in the US and how the normal Orthodox person can support these schools, even if they don’t have a personal connection to them.
As it stands now, a lot of this information needs to be updated before I republish the list; Target, for instance, discontinued their school fundraiser program; Campbell’s soups, which probably had the first big corporate school fundraiser program also discontinued their program (soup can labels); General Mills has completely revamped their Box Tops for Education program, etc.
However, I did find a corporate fundraising program that I didn’t know about that includes a number of Orthodox schools. Casey’s (also known as Casey’s General Store) is a chain of gas stations and convenience stores which currently has over 2000 locations in 17 states – mostly in the Midwest. They have an app (like all big stores these days, it seems) where one can collect loyalty points. The interesting thing, though, is that these loyalty points can be converted into cash donations for schools – and private schools aren’t excluded.
I’ve checked, and there are a number of Orthodox Schools listed in their school directory. Anyone who shops at Casey’s can participate; there is no requirement that one live within a certain distance or have kids in the school. Here’s what it will look like in the app once it’s set up:

The more people who know about these things, the better the chances of higher participation, and the better for the schools.