If the question is "Does level of education correlate with income in the United States?" then the answer is Yes.
Infoplease reveals the Median Annual Income, by Level of Education, 1990–2009 and the table has some very clear jumps as the level of education rises, dropping only once you reach a Doctorate.
e.g in 2008 (last year with full data), man with a high-school completion earns $43,165, compared with $33,435 for starting but not finishing. For a woman, the figures are $31,533 and $21,937 respectively.
If the question is "Do the grades achieved correlate with salary in the United States?", the answer is murkier, but Yes.
Academicians and business people have disagreed about whether grades predict occupational outcomes such as training success, job performance, and salary. Recent meta-analyses have suggested that grades are useful predictors of training success and job performance. Unfortunately, the results of meta-analyses examining the grades–salary relation were limited by methodological problems. These problems included confusing income and salary as the same dependent variable, not conducting moderator analyses, using unorthodox schemes of weighting correlations, and not correcting for research artifacts. The current meta-analysis focused only on studies that reported salary as the dependent variable and found uncorrected correlations of .13 for grades and starting salary, .18 for grades and current salary, and .05 for grades and salary growth. The correlations for grades and starting salary rose to approximately .20 when corrected for relevant artifacts and the corrected grades–current salary correlations rose to the mid- to high .20s. Moderator analyses are also reported.
I haven't read this paper (paywall), and note that it isn't clear about which education level is being analysed here - secondary? tertiary?
If the question is "Do SAT scores correlated with income
in USA?", the answer is Yes, for SAT Math scores, according to an Honors project. (Caution: Honors project may not be to the same standards as peer-reviewed articles.)
This student attempted to model the future income of college students based on a number of variables, and found that their SAT Math score was a significant factor, but that their SAT verbal scores were not.
The results for the math and verbal variables are very interesting. The
SAT math variable is significant in the regression, but the SAT verbal variable is insignificant.
This supports the previous research. It implies that math ability is much more important than
verbal or linguistic skills in most occupations. The results also suggest that math ability is more
directly linked to acquiring human capital than verbal ability. The coefficient for the SAT math
variable is above 10 in the regression. This means that a student that scores a 700 on the SAT
math will make over $2,000 more each year on average than someone that scores a 500.
If the question is "Do high school exam grades correlate with salary in China?", it is complicated.
An interesting approach is taken by
First they show that one year of schooling increases an individual’s earnings by 8.4 percent. Then, by comparing twins, they show that the schooling itself only accounts for 2.7 percent, and the rest are due to "omitted ability or the family effect".
speciﬁcally, we ﬁnd that high school education mainly serves as a mechanism to select
college students, and has zero returns in terms of earnings. In contrast, both vocational
school education and college education have a large return that is comparable to that
found in rich Western countries.
So, doing well in exams may not directly lead to much greater earnings, but just open the door to an education that will.
Correlation is not causation! The income of the parents is a good predictor of a child's SAT scores. No doubt, it is also highly correlated to a child's future income levels.