If schoolwork is MS Office the a Dual is more than enough, the OS is optimized to balance all active apps across whatever cores are available. Even running just a browser your OS is running approx 40 tasks, that are balanced over the multi cores, go to your active tasks window and you will see that there are many tasks running in the background, thats is why at least a 2 core system shines
An E8400/E8500 even an E7200 is so fast that unless you are doing extremely CPU intensive tasks the jump to anything more will show diminishing returns in performance
Future Proof ? I bet the users who paid $500 for a Q6600 to have a future proof system 1 year ago are kicking themselves now, when they could have had a $200 then E6400 or a then $150 E4500 then swapped in a $179 Q6600 today and been $100 - $150 ahead of the game plus had a used one to sell
Also its .76 difference but not one core vs one core system, its 2 x 3.16ghz vs 4 x 2.4ghz, measuring MIPS or TAPP then the Quad has much more processing potential (using that potential is the question) If you do get an app (and they are coming) that uses all 4 cores, and you max out the 3.16 Ghz system, you will see in a blink how much faster the 4 cores at 2.4 suddenly become.
Imagine the instant sales success of the 1st game to truly use a 4 core system, it would fly off the shelves and be a runaway success day 1