Best Time to take Math 1 or Math 2 SAT II (subject) test

My son is currently a junior in high school and his math coursework has been:

8th Grade - Algebra 1
9th Grade - Geometry
10th Grade - Algebra 2/Trig
11th Grade - IB Math 1 SL

He would like to take one of the Math SAT II subject tests. Which test aligns with the work he has done so far and is there any value to waiting until he’s done with IB Math 1 SL to take one of these tests? What topic gaps should he cover on his own?

The more math the better. I’d take them both 2nd semester junior. If he doesn’t like the scores, retake senior fall.

Would you advise taking both Math 1 and Math 2 on the same testing day?

I would advise that he take only Math 2 at the end of Junior year. The curve for Math 1 is brutal while you can get about 9 wrong on Math 2 and still get an 800.

Agree with the above recommendation plus most colleges prefer to see the Math 2 exam.