Schools in Punggol. Socio-economically advantaged or disadvantaged intake?

[limweech]

Channelnewsasia has a report on what PM Lee said at the Teck Ghee Bursary and Scholarship Award Ceremony on Sunday.
http://www.channelnewsasia.com/stories/singaporelocalnews/view/1102333/1/.html

He was referring to the Programme for International Student Assessment (PISA) that tested the reading, maths and science abilities of students.

I looked for "Programme for International Student Assessment (PISA)", and found http://www.pisa.oecd.org/

Just glancing through the summary, http://www.pisa.oecd.org/dataoecd/34/60/46619703.pdf
Page 9 has the following,

Regardless of their own socio-economic background, students attending schools with a socio-economically advantaged
intake tend to perform better than those attending schools with more disadvantaged peers.
In the majority of OecD countries, the effect of the school’s economic, social and cultural status on students’
performance far outweighs the effects of the individual student’s socio-economic background. And the magnitude
of the differences is striking.

what does "socio-economic background" mean? i don't know.. but I suspect it is strongly correlated with income.
Let's look at Punggol 21.. mostly households with combined income of $8000 and below at the time of application for HDB flats. Would this mean intake for schools in Punggol 21 has disadvantaged intakes ? or maybe that's the norm across Singapore, except for notable exceptions such as Raffles Girls' Primary School ? OR are Punggol schools right at the bottom of the heap?