The schools in our district all have business partners. Mostly the relationships are established to provide some educational opportunities in the classroom, but every business partner I know of contributes to their school in some fashion. We have Walmart, JCPenney, and Fareway groceries and they all help us with donations for events and classroom projects.
Each school in our district has a PIE (Partner In Education). Our partner is Plumley Company/Dana Corporation. I am from a very small rural area. (Our whole county is around 10,000 people.) Businesses are very willing to partner. They range from banks to factories. Plumley/Dana hosts awards day each six weeks for the kids, donates presents for the teacher, etc. Employees come and help with lunch at the beginning of the year and during award days. We have a special area of our website in appreciation for all they do. Within the the last 3 weeks we have added PTO to the school website also. Check it out at www.rheaschool.com
I don't think our school has been adopted but we do participate in the adopt-a-classroom program; in fact, we won an award last year for having so many sponsors in our school-15 last I heard. I think the national program suggests $500 per year from a business but we toned it down to less ($100?), although it seems most companies go above and beyond that. Plus, most supply volunteers to help in the school and some even pay them while they're there.
In return they get mentioned often at meetings and such and highlighted on the school marquee, and many parents/teachers try to patronize their businesse whenever possible.
I don't know the details of the program because it isn't run through the PTA but by our Volunteer Coordinator at the school, who is a self-described "noodge" that has been there for years.
We live in a fairly large metropolitan area with many, many schools. The businesses we approached were not willing to tie themselves to a single school. So the concept didn't work for us.
However, I still see references to "adopt a schools" once in awhile. So some areas must still be doing it. I've seen this in relation to companies and to service groups, like college sororities/fraternities.