Here is a link to the Texas Education Agency annual report on YES Prep and their performance on the state exams 16-17.
https://rptsvr1.tea.texas.gov/perfreport/tapr/2017/index.html
On the left margin, click “District Report”
Enter “Yes” in the search box
Select “Yes Prep Public Schools in Harris County”
Click “View Report”

Their performance is really very mediocre.