They are one of the most contentious issues in Scottish education - drawing celebration from some quarters and firm condemnation from others.

This year The Herald has resumed compiling school league tables but, in order to level the playing field as far as possible, we have expanded the data sets we are presenting to try to give greater context.

To compile our interactive table we usually look at the benchmark used by universities of the percentage of pupils passing five or more Highers by the time they leave school. 

The data is not so straightforward, however, as Education Scotland, the quango that publishes exam result, uses the measure of the percentage of pupils from an S4 cohort who go on to leave school with five or more SCQF Level 6 awards.

READ MORE: School exam system is about to undergo changes

All Highers are Level 6 awards but not all Level 6 awards are Highers. We have, therefore, used the number of pupils leaving school with five or more Level 6 awards.

The data also does not tell us whether awards were achieved in fifth or sixth year so schools where more pupils stay on tend to score higher numbers.

Further, we have included the SIMD profile of each school. The Scottish Index of Multiple Deprivation gives a picture of the socio-economic backgrounds of the pupils in a school.

Our table shows how many young people in a secondary are living in SIMD1 postcodes - the 20 per cent most deprived in Scotland.

This is important for context as the schools traditionally ranking at the top of the table tend to have no or very few pupils in SIMD 1 or 2. 

We know that poverty deeply effects educational attainment and so schools with larger numbers of pupils from disadvantaged backgrounds tend to do less well when ranked by the bald measure of exam success.

Many, however, are doing far more innovative work in other areas than the schools in leafy suburbs.    

A far less contentious measure of performance is the "positive leaver destination" figure of a school.

READ MORE: School exam system is about to undergo changes

This is the percentage of pupils going on to further education, training, work, volunteering or other suitable next step when they leave secondary.

Tomorrow The Herald will look at how schools are focusing more on diversifying the timetable away from the outdated notion of Highers at all costs to more appropriate qualifications that suit all learners.

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Schools are all given a "virtual comparator" - a benchmark figure worked out by the Scottish Government that shows how well pupils perform compared to similar schools.

We have included the virtual comparator for each measure to show how a school is performing relative to expectations. 

The Scottish Government withholds data when it could be used to identify individual children. 

In this context, some schools are marked “c”, meaning that there were either too few children who earned five or more awards or who moved on to positive destinations or too few who did not.

READ MORE: School exam system is about to undergo changes

A Scottish Government spokesman said that some schools were marked with a “z” which means that there are no applicable statistics. 

This could mean that schools did not report the data, or that there weren’t enough pupils at a certain grade level.

School leavers in west of Scotland schools once again dominated the top of the league table with eight out of the 10 of the schools in the west of Scotland. 

East Renfrewshire, as usual, dominates the league table with four schools in the top 10 while East Dunbartonshire comes just behind with three schools. 

Jordanhill School regularly features at the top of the table and does so again this year but has no pupils from SIMD1. 

READ MORE: Why school league tables are no way to judge a school

We know that poverty has an impact on attainment from the very early years onwards, meaning pupils from fall behind in terms of literacy and numeracy, and can struggle to catch up.

This means schools in middle class areas tend to sit at the top of the league tables and many in our top 50 have, like Jordanhill School, no or very few pupils from SIMD1.

It therefore makes the achievements of schools like Glasgow City Council's Notre Dame High School with 43% of pupils in SIMD1 even more impressive.

By comparison, some schools towards the bottom of the table have as much as 90% of young people from SIMD1 postcodes. 

Critics rail against league tables as being narrow and misleading because they focus on one specific measure and fail to tell parents anything useful about the wider context of a school or the supports on offer to pupils. 

It is important not to read the tables as suggesting that those at the top are "good" and those near the bottom are "bad" as this is not what league tables tell us.

Education Scotland has worked to try to prevent facile comparisons between schools by publishing the data on an individual school level, rather than in table form.

Our table makes simple comparisons much easier for parents but should be read in conjunction with inspection reports and other information about a school's pastoral care and extracurricular activities.

The league table is the beginning of three days of coverage of Scottish exam attainment. 

FRIDAY: The Herald investigates school leaver destinations and why the metric is the benchmark of the future

SATURDAY: Inside a Scottish school at the "bottom" of the league table