Check out this article in the hometown Strib discussing the success the local KIPP school had in bettering test scores after expanding the school day and implementing Saturday school. I've been an advocate for this, ever since I saw the episode of West Wing where Congressman Santos explained to some parents in New Hampshire that the basis for our school year and school hours were based on agriculture and industrial societal models that needed child labor to help on the family farm or supplement family income by working extra hours in the factory. However, since this is no longer the prevailing societal model then it makes sense to change the educational structure that was put in place to support a now non-existent model.
What also drives my support is hearing, ad nauseam, about how American kids are falling further and further behind their Asian and European counterparts. Since America's station in the world is due to it's ability to technologically advance (and monetize those advances which in turn feeds our political stability and military might) faster than its competitors you would think we would do all we could to ensure our next generation of technological 'advancers' were on par educationally with their Asian and European counterparts.