High School Mathematics
Mr. Senter's MATH:
Here are some links to specific content in Khan Acadamy that may be helpful.
Algebra 1 - Freshman
ALGEBRA BASICS
https://www.khanacademy.org/math/algebra-basics
Geometry - Sophomores
BASIC GEOMETRY
https://www.khanacademy.org/math/basic-geo
Algebra 2 - Juniors