Scottish schools are inspected, but less frequently than English schools so a lot can change between reports. You might have to cut and paste the links.
www.edinburgh.gov.uk/info/20074/schools/1006/school_inspection_reports
You can also dredge up data on attendance and other factors here.
www.gov.scot/Topics/Statistics/Browse/School-Education/AttendanceAbsenceDatasets
Table 3.1 is attendance by primary school that notes e.g. truancy and exclusion. You'll want to better with excel than I am with clicky links. You can sort the data so you only see Edinburgh schools. The data doesn't paint the whole picture of course, I took attendance to be the most relevant, suggesting parents motivated to support their children's education. I had a quick peek and on the face of 2014/15 and all other things being equal, if I had the choice I'd go for Liberton to be fair (78 exclusions versus 5, 50 very lates versus none, could be one or two challenging kids racking the numbers up). That's not to say there aren't loads of happy kids doing really well at Gilmerton though, and an amazing bunch of teachers as well.
I also looked at school websites, for us breakfast clubs and after school were important. Might not be for you. Of course some schools might be busier arranging fantastic extra-curricular stuff than they are at putting it on the website.
If you're lucky the parents/parent council/PTA might have an open Facebook group, you can nosey what they're chatting about.
It is also not unknown for a prospective parent to come to a school at pick up time and chat to existing parents to find out what they think of the school.
It feels like such a huge decision, as we all want to do the best we can for our kids and starting school feels like such a huge step. But I bet whatever school you look at most parents would say they are happy with it.