I think money can go further in poorer countries, but distance and language can be a barrier. There also need to be resources in the schools and hospitals themeselves. So yes, buy and send them books, but also, fund libraries, and books for those libraries so everyone can access, and librarians, and teachers for those schools.
I am reading about one called Room To Read.
however you can sponsor a child in your own country for about the same amount and also do mentoring where you can bond..college students can do this with a poorer child, who may not have the even considered the prospect of going to college because its so expensive, even though they may be bright.
Charities like KidsCan, and HIPPY
compassion International sounds a bit like TearFund, which I know is a christian one, while Childfund was open to all
I think if you are able to sponsor a child for the long term in another country that is great, but if you really want to BOND with another child, foster, adopt, mentor or sponsor one in your own country.
its girls who most desperately need education as many are denied that opportunity in poorer countries. You may want to check out charity navigator that rates the transparency of charities
those who have a challenge grant model are ones where the community puts up or is willing to put up half and the organsiation then meets the other half, this works as a hand up rather than a hand out.
I know childfund did things like...build toilets and provided goats, chickens, seeds etc for the whole community, not just money for the parents/guardians to spend on childs birthday presents and food. While that is important, I think to get out of poverty girls need education the most, which is NOT free in many countries.