[anoved]

I'll let others address your actual question of increasing speed, but I'd just like to make the [perhaps obvious] point that speed isn't everything. I'd argue that comprehension and composition (diction, logical structure, etc.) are more important than unqualified speed.

[skn]

I second that. One of the drawback of writing slow, is that children often miss what's written on the board and unfortunately at times, teachers forget this.