I teach far lower down the school (Y1) but I guess the principles are the same. I tend to set a similar task across the board, but would have more support for the lower kids (often in literacy a TA or myself will work with the lowest group and scribe for them), and I differentiate with their targets. So I might say "X group need to write at least 2 sentences, thinking about including capitals and full stops, Y group need to write at least 3, and as well as full stops and capitals need to include the word because in both sentences". Each child has their own targets too (obv differentiated) so I go round whilst their working, check they know what their target is and remind them to do it. I think sometimes in literacy differentiating by outcome is fine....I feel that if I set completely different tasks for each gorup, the middle group (for example) may miss out on attaining higher as I haven't given them that chance.