Child labor is probably better solved by paying kids for good grades in school. The ones getting an education would be less likely to divert effort to jobs that might take away from study time, even after they turn 18, while the ones who aren't getting an education anyway could at least gain some work experience and bring value to their families. This would also greatly reduce classroom disruption by "students" who are not actually learning.

For example: $1000/year for a D, $2000/year for a C, $4000/year for a B, $8000/year for an A. (probably better to use national test score percentile though)