Does he have an interest in taking the SAT? My kid took it just for the experience (in 7th & 9th grades) but back then the tests were in-person at a high school, so just physically experiencing what that setting was like was an element we thought would be helpful. And the scores were too “old” to be used as confirming scores for the NM/PSAT so they took the SAT again in 11th grade.
One thing my kid noticed was that the SAT in math is more geared to a more typical math progression, so the math part was actually easier in some ways in the younger grades since my kid had already covered (10th grade) Geometry and (11th grade) Alg 2 by 8th grade. By the time they were in 11th grade and doing mostly calculus, they had to review a lot more of the “old” material in order to prep for the math portion of the SAT.
If he wants to take it, I wouldn’t discourage it (well, obviously I didn’t with my kid) because I do think it’s helpful for a student to experience the mechanics of taking the test without the pressure of having to perform well on it. So at least that factor doesn’t have to be a stressor for the real sitting since they know what to expect.