It's a good thought, but you gloss over many things. First, not everyone has a good computer or Internet access. Second, can you imagine the support nightmare? I went through an online Masters program through a good school and it was almost impossible to get everyone online at the same time with working video conferencing. Tons of problems...tons of issues... Now add in to that people that just want their kid to go to middle school and you're setting yourself up for a lot of missed homework because the computer was infected..or Word kept crashing...or the Internet was down...etc.
The only way this works is to do it in parallel with traditional processes, which many schools now do. We're not at the point where we can cut over to all electronic communication just yet. I'd love to...but we aren't there yet. My son's preschool does a good bit online but many forms and other information still come home on a regular piece of paper.