Weaknesses:
Selection bias. Only juniors and seniors are surveyed when there are some sophomore students who are currently having a job.
Response bias. The response samples may lie in the surveys. That is, I cannot determine whether the responses are truthful or not.
Non-response bias: There are many who did not return the surveys. Consequently, the sample size for male proportion is too small, thus produces inaccurate results.
The study only extrapolates to the suburban areas. We take transportation as the reason. Maybe more students in the cities are working than those in the rural areas because they have cars or they are closer to the working area.
Sample more high school students in the other areas. Since the minimum age of work is 14, the study will be more accurate to include also the freshman and sophomore groups. Also sample more students next time to make sure the sample size is large enough for the test. Finally, a homogeneity test is more preferable since the surveys we see that there are more students working than not working for both male and female students.