Personally, I'd like to change the "feel" of school more than anything.

As it is, the emphasis in grade school is on rote memorization and rigid structure. Aside from art classes, there is little or no actual critical or creative thinking done in the current public school system. It's mostly a shut-up-sit-down-memorize-this-and-repeat-it-on-the-test approach.

There should be more emphasis on what the kid is interested in, and more personal projects. Core classes should be math, english and science, and everything else should be an elective (with listed pre-requisites).

As for the approach, science and math should be taught at a more conceptual level.

It's not as important to memorize a particular result of science, as much as understanding the overarching philosophy and methodology of the science.

For example why not compare two theories (say evolution and so-called "Intelligent Design") how they fit the available evidence. Identifying science and pseudo-science is never really addressed in the current system. The fact that so many people think ID is a real science shows that we've spent time on details rather than the big picture.

Also, I think some classes should be "free form"... and basically defined by the interests of the students.