Shelly,
According to articles like
this one, factors that favor a bone marrow transplant include severe aplastic anemia, age under 10, and a matched donor, particularly a matched sibling. The statistics show great success for transplants in these children.
ATG is nearly as successful, and may be recommended as first-line treatment for less severe aplastic anemia or when a donor isn't available. What leads you to say that the ATG response rate isn't good?
You might it useful to refer to Table 1 in
this landmark article, which covers both adults and children.