<Mounting the soapbox>
In my experience (such as it is), when differentiated work for GT students works, it's usually as simple as a bottle of white-out and a "x" sign.
It's all but free, quick, easy, it doesn't even require great creativity, but it makes a HUGE difference to a kid...
<stepping off soapbox>
And it did make a big difference to DS. As DW and I started talking to him explaining why we met with his teacher (to get more appropriate work for him) and that he may go to another school (he'd be bussed once every 6 days for the pull out program) to learn other things, he coined a new term. How did he put it? It was something like "is that I-don't-know-stuff or I-know-stuff?". He got very excited when he found out that he'd start getting "I-don't-know-stuff".
JB