I don't know that one or two weeks missed per year have that much of an effect.
The problem is, the research says it does. If we argue that government policy is based on flawed research, where do we stop? What other legislation is based on research that someone, somewhere, doesn't agree with?
The smoking ban in cars with DCs, for instance; based on research that passive smoking can be harmful. But, plenty of children grew up with parents who smoked and don't have health problems, and lots of parents still WANT to smoke in cars, so they say the research much be flawed and the government are being heavy handed and controlling.
What about speeding? Research shows that higher speed kills. Speed limits have to put in place to protect lives. But I want to drive faster in built up areas, so I don't accept that the research is correct.
If there is independent evidence that something is detrimental, and parents don't take steps to protect their DCs, then the government has a responsilbity to legislate, doesn't it? Or, should society be left to screw up the next generation, unregulated in any way?