BeenBeta - I agree that the students should be tested, and I would like to see end of year exams in all subjects, so that the students get used to exams and exam conditions, and thus it is easier in Year 10.
However, SATS don't test right across the curriculum, but just in 3 subjects. When a child came into my classroom, I didn't look at the SATs data, which only tells me how they performed that day, but at their GLA; how well they could read was key for me as the subjects I taught in secondary were text heavy.
The other reason I want SATs scrapped is that they stifle learning. DS did them, and spent from Oct 06 to May 07, when his school did SATs, doing nothing much but practice papers and being drilled for the exam. This is a term wasted when they could have be doing a much broader curriculum.
Teacher assessment will tell you much more about progress than SATs will.