Saint Stephen's uses the Eureka Math book series.
Some of the topics covered in Grades 6 through 8 are listed here.
6th: Ratios, number theory, arithmetic operations, fractions, area, surface area, volume
7th: Equations, expressions, percent and proportion, probability and statistics, geometry
8th: Exponentials, linear equations, geometric and linear functions, irrational numbers
Eureka Math books digital versions: www.engageny.org and www.unbounded.org
Eureka Math website with parent resources: https://greatminds.org