That is an amazing and very inspiring adventure! While I haven't really seen a school with such condition as you described it, I can somehow relate with what I have seen in our country.
Volunteering is indeed a very memorable experience. The bond you establish with the beneficiaries is priceless. Add to that the impact of what you did to their lives. It will be a good memory to reminisce and recall that in your own way, you have been part in shaping the future of the children there through having them educated in a decent facility.
Keep blogging about inspiring adventures! And may those blogs inspire others to do the same.