Thanks for following up on this. You're absolutely right that a pupil might start making progress towards some new objectives, but having not secured them yet, their Average Depth measure may go down. Average Depth, and the other objective summaries, weren't designed to be used in isolation because of issues like this.
Finding one number which accurately represents various types of progress in different years/subjects and for different types of pupils, is very difficult. Talking about progress at this detailed level in Insight is designed to be more conversational, taking the different pieces of information into account. For example, although Average Depth would have gone down, their % Covered would have gone up.
That said, schools have come up with alternative options, which are worth considering:
Some schools are making teacher assessments of progress alongside their teacher assessments of attainment (eg Small Steps, Steady, Rapid). This is an elegant solution which puts the final say with the teacher rather than a formula, if you don't mind the extra assessment workload.
For schools using objectives, some are using different summary data points to help them talk about progress at this level. For example, you might want to see the total score, rather than the Average. We're able to add different types of simple summary to help you look at the data in a way that makes sense to you.
Some schools are using P Scales grids or similar to track smaller steps of progress for children who are working below their curriculum year. This can be a good way to get insight into what these children can and can't do, despite them remaining 'Well Below' on the main curriculum grids. We've seen schools using PIVATS, B-Squared and other systems, either to enter formative assessments (but do consider the workload!) or to enter a summative grade to show individual progression for these pupils.
Would really appreciate your thoughts!