The US child labour law is generally considered one of the strongest in the world in preventing minors from working in dangerous industries. But the agricultural sector is a lone exception. On farms, children as young as 12 can legally work with parental approval. And many other children, younger than that, are often found in the fields working illegally. Nobody knows the true number of children at work in the fields, but farmers reported hiring over 200,000 children under 18 in one year alone. Migrant farmworker families are often so poor that they have little choice but to have their children at work harvesting crops. In effect, their children miss school, change school districts, and fall behind in their curriculums. A large majority of migrant children will not graduate from high school or college and will likely fall into the cycle of poverty where they themselves will be working in the fields to support their families. For years, the federal government - both Congress and the US Department of Labor - have considered legislation and new regulations that would raise the legal age for children to work on farms. This was done with migrant children in mind, but the proposed measures have been largely unpopular. Lobbyists for large farming interests and US congressmen have successfully pushed the bill off the national agenda. The American Farm Bureau says the proposed rules are too broad and would put harmful restrictions on American family farmers. But in rural communities across the country, farmworker advocates are fighting back on behalf of migrant families and their children to protect them from labour practices they say are harmful. Robust federal migrant education programmes in US schools have supported children of farm workers trying to help them graduate. Fault Lines travels to the onion fields of Texas and the tobacco fields of Kentucky, to investigate how child labour affects migrant families, and who benefits from their work.

We live in a world run through with Fault Lines. Al Jazeera's Fault Lines takes you beyond the headlines and holds the powerful to account as we examine the US' role in the world.