。
She takes pride in her high school.
Literal
She [topic-は] her own high-school [object-を] pride [as-に] is-doing.
誇りにする ('to take X as one's pride') frames her high school as a source of pride. School pride is a significant cultural element in Japan, where attendance at a particular high school often signals academic level and future trajectory; alumni can retain strong loyalty to their 母校 ('alma mater') for life. 高校 is the standard abbreviation of 高等学校 ('senior high school,' grades 10-12).