Rather than look for a big organization, where your donation would get lost in the millions they already get and your effort would get lost among corporations that can make a greater effrort, perhaps you could look for an individual, perhaps supported by a church, who is in need of money to complete a project already underway...
Like in my church we have a missionary that can supply medicine for a few cents to people in Africa to treat eye disease to prevent blindness. And they can tell you for every dollar you donate how many individuals can receive treatment. You are sure that your dollars are going directly to this cause and can present to your class the actual face of a person working directly for your cause.
We have another missionary working to establish a school in Spain, not a religious school, but a traditional school in a poor area and needs money for desks and lockers. She can tell you how many desks and/or lockers are purchased for a certain amount of money.
I think that's cool.
Just an idea.
