How Do You Backwards Plan for Lower Years?

In the UK our GCSE exam was changed a few years ago so nobody had any exams to go off. Having having a big batch of those final summative tests is really beneficial. How does that play out for lower years? I've done a bit of this in the schools it's I just keep on going backwards basically. You know we've identified what our year twelves need to be successful and then you work your way back from there.