With the current patch for WoW, you don't have a choice as far as spell ranks go.
Your toon will always cast the highest rank of a spell that it knows.

So /cast Lighting Bolt(rank 1)... will end up casting your highest known rank of Lightning Bolt every time.
The only way to force it to cast rank 1, would be to never train rank 2 or higher.

For a two-box set up, that looks decent.
I'd consider changing the Elemental Shaman from Earth Shock to Wind Shock, if the purpose of the shock is an interrupt.
Wind Shock interrupts just like Earth, but also lowers threat a little, which would tend to keep the mobs mainly on your melee shaman.
If the shock is there for your highest damage instant cast, then Earth is the better choice.