A few months ago I engaged in a conversation on Twitter over measuring students progress from KS2 to KS3 and that the data that we were using was flawed as it was not really based on them from a practical point of view, (in particular PE in my case but this does apply across other subjects)
When measuring progress we were seeing big differences in targets and predicted and on analysis it was fairly obvious why.
Now there is a bigger issue here that I wont go into too much detail over but there is a view that in PE we should measure their practical ability?? Sport actually covers so much more than this, from leadership to healthy lifestyles. Do these get graded? Can you make progress in these areas? Which ever way you look at this aspect it is clear that KS2 data does not reflect any of them so progress against it is always going to have questions against it.
The solution!!!!!
The idea that came up through conversation (and there are schools that currently do this) is to assess in some form at the start of Y7 and to then set target grades based on that. In this way you have a better picture of the students that you have in Y7 and a clearer idea of what needs to be done in order to improve.
What I proposed for our department was to build in an induction programme that looks at the full range of activities in the curriculum as well as a full range of concepts and processes. Over the first 6 sessions in PE all teaching staff in PE will moderate and look at the cohort we have and give an assessment based on the activities covered. Though this is still going to be a fairly crude measure the hope is that it will be more accurate than the current model.
Hopefully in using this system we will be able to plan interventions better and highlight where we have issues as a department. This should work in all subjects that have a practical focus, in talking to other subjects such as Art and Drama it is clear that they have similar issues.
Thanks to all the PEgeeks that helped me with this vision, as always you continue to support and inspire.
T&L Nuts and Bolts 
What activities do you assess them on and how do you standardise this?
We are having the same problem, our data is showing that student needs to be 2 levels above where I’m currently levelling them. Our head of data basically says that we have to get them to their target, clearly never going to happen.