In the old days at the end of the year you sat a test and the score for that categorically determined what set you went into for the next year.
To be honest that is how I thought it worked now as well, but I've been advised that there are smaller tests during the whole year and these count too, but are not given a timetable (afaik) for when these tests occur, what weighting they hold or what they will cover. Is it unreasonable for me as a parent to expect that information to be made available/clear to myself or my dc? If you think it is, please could you explain what the downside of it would be? What does your school do?