We sponsor a couple of children in our home country each year through a charity organization. The sponsorship covers their education and daily meals. In the past, we did not use our Zakat money to sponsor the children. Can we start sponsoring them from our Zakat money?
In order for you to give zakat to these children, you would need to ensure that they are (a) zakat eligible (which they likely are) and (b) that the wealth you are giving actually enters into their possession.
Giving zakat to an organization to fund the educational initiatives of poor children would not be valid as there is no transfer of wealth between the one giving zakat and the recipient of it. However, giving zakat in the form of food, clothing, and other such items of wealth to these children is valid provided that it enters into their possession.
In situations like these, it is best to discuss the matter with the charity (Zakat) organization you are dealing with to see whether they can act as agents on your behalf to give zakat to these children. Thus, they could act as your agents in buying clothing or other items of wealth for these children and then giving it to them with the intention of zakat.