Chiri chirping in
It's a difficult one. When you have a smallish amount of money to donate it is often best to put it through an existing organisation that has a proven track record. You as the donor would need to monitor it to some extent, to ensure it has gone towards the agreed items/activities.
The other choice is to set up something yourself, but this involves a huge amount of work, and for a new venture to be worthwhile, a lot of money needs to be involved, and you end up incurring your own admin expenses anyway.
I agree that addressing the causes of poverty and looking at long term solutions is preferable to the short term, small scale band aid effect, but when it's a small amount of money it might be the only thing you can stretch to. Books for schools, outings for kids, that sort of thing?
I like the scholarship idea. Maybe it could be extended to other sorts of courses in areas that are relevant to the local economy, not just English. Small business development? IT? Crafts? Tourism related training? Vocational training of other kinds? Does anyone have contacts with training institutes people could go to? It's also necessary to provide the fare and lunch money, as well as the course fees. Who would choose the beneficiaries and how? Some sort of committee combining expats and locals? What would the criteria be?
My other concern is that the expat areas get a lot of attention and there are many parts of the country away from the tourists and expats where the schools never get the sort of donations the others do. Again, difficult logistically, but worth considering.
My votes would go for the most simple and effective option which is to put the funds through an existing organisation or the more ambitious but compelling scholarship idea, if it could be properly administered.