I think apart from the formal school curriculum being taught in schools, it's even more important to have some extra time with the kids, this one won't be a formal setup kind of, rather a open discussion which i will consider informal setup, this way kids seems to assimilate and learn real fast.
I was with 
- As seen on the white board is mathematics lesson, teaching the kid some basics, differentiating between circumference,diameter,radius,sector,segment,arc,quadrant using the school textbook as the guide.
I feel teaching a big class, a good number of students might not be ideal as the teachers don't really have time to access the weaknesses and strength of the students except through the test and exams.
Thats why individual teaching is quite helpful as it helps focus on a particular student, knowing his weaknesses, identifying them and helping improves that area.
In this case, we make a graphical representation of things we are teaching, the radius,sector,segment,diameter,cicumference,semi-circle, this way the boy catch up really fast.
It should also be noted that examination is not a true test ones ability, most of the times the pressure that comes with exam and test, the students just want to pass at any cost without even necessarily knowing what being taught but extra curricular activities tend to exercise the kids brain more and help their course of learning.