I might meet in the middle--rehearse the first eight bars or so, to get them off to a good start (and this is where they will most likely always start practicing anyway).
Then skip to the end. Work your way forwards and backwards to the middle. Often, students will learn the middle stuff in order to get to the end, which they know.
You could always try doing backwards with one piece and regular with the other and compare your results. I know it's a bit apples and oranges, but see which one fits you and your group best.
Personally, I always hated starting from the end. To each his/her own!