To me ‘formative assessment’ describes all those processes by which teachers and learners use information about student achievement to make adjustments to the students learning that improve their achievement. It's about using information to adapt to your teaching and adapt the work of the students to put the learning back on track - if you like, to make sure that the learning is proceeding in the right direction and to support that learning. It’s what happens when you don’t just lecture students and rattle through the material until you get to the end and ask them if they’ve understood it okay - it’s constantly making those adjustments.
One of the ways I like to talk about it is: just imagine what would happen if a pilot flew like many teachers assess. I flew back from Seattle a few weeks ago - just imagine what the pilot would have done - he would have flown east for 9 hours and then after 9 hours he says 'Time to land'. He will put the plane down and then he will ask 'Is this London?' and of course even if it’s not London, he says 'Well everybody has got to get off because I’ve got to get on to the next journey'. And that’s exactly the way we have assessed in the past - we teach students material and at the end of that teaching we find out if they have learned it or not. And if they haven’t we say 'Too bad, because we are on to the next unit'.
What formative assessment does is it encourages teachers to take constant readings about where students are just in the same way that pilots takes constant readings about their position. If the learning isn’t proceeding as you had planned then you make adjustments - that is the essence to weighing formative assessment. The reason why I think that formative assessment is the right focus is because assessment is the right bridge between teaching and learning. It’s only through assessment of some kind that you know whether what has been taught has been learned. That’s why I think this focus on this assessment process, minute by minute, and day by day, not at the end of a sequence of learning, minute by minute, and day by day. It allows teachers to reflect on their practice and make small steps in improving that practice in a more powerful way than anything we have seen before.