Read them but do take them with a pinch of salt. Ofsted reports are good, but do note that many schools do go to great extremes to ensure that they get a good ofsted. I know of teachers who would teach these amazing lessons for ofsted, and get their grade 1s etc but never taught those type of lessons rest of the year! Whereas there are the miserable sods like me, who don't play the system so much, and do an enhanced but pretty much standard lesson and only ever get grade 2s. I even know of a few teachers who actually taught the lessons to students a few weeks before Ofsted came, so that they had the perfect lessons when they were inspected! I know of one school that spent over half a million pounds preparing for their ofsted report - cleaning it up etc, but it paid off as they got their excellent ofsted report and now things are back to the same as they were before Ofsted came!
I would also suggest you listen to the views of parents, but do be aware that these views can be outdated. Again, I know of a school, who had the reputation for being the best in the town and the one that all respectable parents tried to get their kids into, but the reality was that a fast expansion of the school meant that it had gone downhill quite quickly and was nowhere near the school it was a few years before, but managed to coast on its reputation for quite some time. Equally, a school can have a really bad reputation and that can take a long time to change even though there may be a new head and things have been turned around.
Also bear in mind the socio economic status of the catchment area... when comparing GCSE results and the like remember that a 'middle class' state school usually does better than one in a working class area, but that does not necessarily mean that the teaching is better. I know of a school whereby it has had fab GCSE results, but that's because parents pay a premium to live in the catchment area, and the kids tend to be really bright. If you had looked more carefully into their Alis predictions etc then school didn't actually do as well as it seemed at first sight.
All in all, it is a bit of a minefield, and I personally think nothing compares with going with your gut instinct from viewing the school (but not on open days when the school is on its best behaviour!)