but it could reduce the drop in productivity the parents have when they leave work to pick them up? (just brainstorming). OR it can provide for more customized learning/hands on experience for the individual kids.

I'd argue if we better utilize the hours kids spend at school right now we can do all that without needing more hours.

oh i agree, but if we aren't increasing funding for education, we're unlikely to ever see any change. we as a society don't seem to place education super high on the totem pole come funding time.

7 to 8 hours is probably too much organised schooling, already. However, there's an argument to be made for letting kids stay on the premises in a semi supervised environment after hours.

There's lots of resources available in school which could be useful; you can offer some activities (but please, not an additional 5 hours on top of 7 hours of school), or help with homework (dito), and generally offer an environment that's hopefully more conducive to learning in the broadest possible sense than some of the worst home/street environments.