Let’s focus on the underlined part in (1).
(1) And when more students said they didn’t like their school, the percentage of smokers in the student body [color=red]also was higher.
“Also” suggests the same thing applies to something else. In view of this, the part at issue can be paraphrased as “[color=red]the percentage of students who said they didn’t like their school [color=red]was higher.”
Do you agree?
Thank you in advance
Seiichi MYOGA