Math
Note: These are just recommendations. All courses and their descriptions can be found here.
For math courses, this site recommends taking Adv. Algebra II in 9th Grade if possible, or, if it is not, taking Adv. Geometry. Taking Pre-Calculus (Known as PreCal) in 9th Grade leads to much harder classes later on, leaving a larger negative impact on GPA. Taking on-level math courses is not worth it, for they teach the same material at a slightly slower pace while greatly negatively impacting GPA.
When possible, this site recommends taking AP math courses. Additionally, this site recommmends taking Calculus as close to college as possible. If you wish to take AP Statistics, you cannot take it between Algebra II and PreCal unless you take it with either simultaneously.
IB
If you wish to take IB, then I would recommend taking the IB Math Analysis courses after you complete their prerequisites.
Ranking (Easiest to Hardest)
Note: IB courses, AP Statistics, and Multivariable Calculus are not ranked below due to a lack of knowledge. Please send a review to abhiram.donepudi@gmail.com if you are taking IB courses or know something about them.
Algebra I
Ranking: Easy (Only on-level is available at Westwood)
Algebra I is a very easy course for students in math, though this site would not recommend taking it in high school because of the negative GPA impact (it is on-level).
Adv. Geometry
Ranking: Easy-Middling
Geometry is easy for most students, but for students that are weak at math, it can ruin their GPA. If you think you are one of these students, this site recommends doing prep for Geometry before taking the course.
Adv. Algebra II
Ranking: Easy-Middling
The creator of this site found Algebra II an easy course, but, for others, it can ruin their grades insanely quickly. Be sure to learn topics beforehand if you wish to excel.
AP Pre-Calculus
Ranking: Very Hard
AP PreCal is famous for ruining students' grades, but it does have a very easy AP exam. Some students find it better to take on-level PreCal due to AP PreCal's difficulty. Like mentioned before, learn topics beforehand to excel.
AP Calculus AB
Ranking: Middling
AP Calc AB is a hard course, but it is manageable for most students. It is a good introduction to calculus and is recommended for students who want to take calculus in college.
AP Calculus BC
Ranking: Hard
AP Calc BC is also a hard course, and it is less manageable for than Calc AB. It is also recommended for students who want to take calculus in college.