I heard that supporting your own children over the age of six can possibly be counted as maaser. Does this include paying for transportation for them to go to school or it does it only include basic necessities like food and clothing?
The question of going to school is delicate, because maaser money cannot be used for paying for obligations. A person is obligated to teach his children Torah, and this obligation includes the transportation to school, if this is the only method of getting there.
Therefore, under normal circumstances one should not pay for the transportation to school from maaser money.
One should likewise not use maaser money for the basic requirement of a child, because there is an obligation (at least by dint of the universal custom) to provide a child’s needs until he is grown.
For sources on this question, please see here, para. 1-3, and attached sources.