Honestly? I avoid them like the plague! Working in a three-tier area, we had a phase of secondaries thinking it would be a great idea to create bridging units to aid progression. Unfortunately, they have one major flaw: either they're too narrow in outcomes, and so restrict higher ability students and miss lower ability ones, or they're so open that it's impossible for the high schools to make much use of the information in them short of reading every single one. And if they're going to do that, they might as well just look at their "real" work. The kids didn't enjoy any of them, and actually for those kids who were ready to make the break, they didn't want their old work following them. Add into that the administrative nightmare of passing work on, making up sessions for absent children, etc., - overall, the work that went into them by staff at both sets of schools was far greater than the benefit. I'm not sure from your post if what you're looking for is ways that secondary teachers can help primary teachers, or ways that secondary schools can help transferring students. They are very different things!