I typically don't jump into keyboarding instruction until sometime in the 3rd or 4th grades. Occasionally, given compelling reasons, I may start earlier. The biggest predictor to keyboarding success is consistent exposure. I will generally recommend 10-15 minute skill drill 3-5 days per week, with the idea that learning to keyboard is a process.
To support this process, I want to tell you about a free online typing site. KidzType is an amazing site filled with great instruction and games for reinforcement.
KidzType touts the benefits of touch typing, and that is the focus of the instruction. However, even for folks who are entrenched in a hunt & peck method, or single handed typing (secondary to a physical issue) the site can help users increase both speed and accuracy.