Hey Herald. So "children in bigger classes and bigger schools get better grades", hur?
"Children in bigger classes and bigger schools get better grades" implies a relationship between these two things. This kind of relationship, if it's strong, might look something this:
On the other hand, if it's a weak relationship, it might look something like this:
This is what your relationship actually looks like (courtesy of DimPost):
Note the R^2 value. What does it mean?
The closer the R^2 value is to 0, the poorer the fit. Your R^2 value is 0.137. If we take out the special schools, that goes down to 0.0738. This is what we would call a "poor" fit.
If you would like to learn more about statistical interpretation, please read the following books:
I don't know what this "NCEA" thing is, but I hope that, one day, they'll start teaching it in schools.