Real Differentiation

Do you ever feel that you were cheated by your initial teacher training? Some of us are unlucky enough to have felt that way while still on our training courses, while others had to wait until they were in the field to reflect on the essential tools they were never introduced to. For sure, developing mastery in teaching comes with experience, but one particular feature of teaching that I am constantly surprised at the lack of attention to is differentiation. 
I was among the more enthusiastic learners in my teacher training cohort and yet I graduated with the very puzzling impression that differentiation meant double - or even triple - planning. How this was to be achieved, it was suggested, we would figure out along the way. When staggering under the workload of heavy timetables, constant (and rather pointless) administration, challenging (euphemism!) student behaviour and constantly shifting curriculum, I could only be thankful that at least my classes were streamed and there was a comprehensive bank of tried-and-tested unit plans that I could dip into.
Years later in the context of mixed-ability classrooms (which I now firmly believe in), I finally started to realise what differentiation is and, more importantly, what it is not. As already pointed out by others, differentiation is not about planning more, but planning differently.
For those interested in readings, Tomlinson and Marzano are really the anchor starting points and they very helpfully provide concrete examples across a range of ages and disciplines. Since implementing suggestions from these heavyweights (among others) I no longer 'teach to the middle' and have evidence of real gains among my learners. Those that I worried about not being challenged enough indicate in their reflections and feedback that they thoroughly enjoy the new 'intellectual stretching' on offer, while those who tragically became used to failure as part and parcel of their classroom experience are visibly excited to progress from one task to the next.
Admittedly, it is not a panacea - no one strategy alone can be in my opinion - but getting my head around this not-so-complex methodology has given me practical strategies to reach every learner every time. Not only does it build on my philosophy of 'voice and choice' in learning, but it also makes the whole concept of personalised learning manageable.
In the interest of developing discussion particular to my teaching context of English (Language Arts), I have created an Edmodo group which can be joined by clicking here.
For those looking for some practical strategies, I cannot recommend the Dare to Differentiate wiki highly enough as a source of practical resources that get you started within the hour, but I provide the link with a caveat: take some time to read the literature around differentiation first because otherwise you may not see the value of the tools you find. It was certainly my reading that opened my eyes to the employment of known materials (such as graphic organisers) in new ways.
If you, like me, had considered differentiation as something that you perhaps already did as well as could be expected, take a second look: you might find something new to enhance your own ideas and add to your teaching toolkit, and with it a renewed vigour in your classroom.