This is exactly how they are helping the US economy. We spend 11,000 a year to educate a kid in the US public school system and probably another 11k per kid that the parents kick in. If you dump the kids off in Nicaragua, you can spend probably one tenth that much.
A lot of these parents are being paid under the table. Even the ones who aren't aren't putting anywhere near enough money back into the economy to pay for education, health care, and other various public services. It's just not happening.