A good place to start is the financial aspect of a schooling institution. With a detailed account of school's spending we can actually get a lot of information – from the number of students eligible for free lunches or the amount of school's grant funding to the sums allocated in educational equipment or the average expenses per student. Having at hand both current and historical figures, we can easily detect the school's financial interests and thus predict its future development – is it going to focus on providing its pupils with higher-quality meals or modern schooling facilities?
Another important point is the school's performance on key level tests, which indicate the teaching level and efficiency of the schooling institution. Depending on our focus, we should be able to access both general data and scores by subject – thanks to which we can divide school subjects into those that are taught on an average level and those that surpass the average scores. Some historical data would be useful too – judging the scores from previous tests we can trace the school's development or deterioration in general or in relation to specific school subjects.
A different, but equally important indication could be the school's census data, which, among others, shows the percentage of students whose first language is not English. If you've just arrived in England and are worried that your children might find it difficult to get accustomed to the new language and culture, you might want to consider enrolling them in a school attended by many children of mixed ethnic background. This might help them to settle in the new environment and ensure that they grow up to become open-mined and respectful of other cultures.
To sum up, data can often speak for itself and thus considerably facilitate the process of school choosing. The only problem faced by parents is its accessibility, but since we live in the so-called digital age that offers many opportunities for an easy communication, the creation of special online resources (e.g. http://www.bbc.co.uk/schools/ or http://www.eduexpress.co.uk) devoted exclusively to education should be a viable option.