The best advice was given to me – many decades ago – by my chemistry teacher.
He told me that even though I was a 10th grader and hadn’t taken the SAT yet, I should consider taking what were then called the Achievement Tests (now the SAT Subject Tests) at the end of that year because I was likely to do well on the one in chemistry.
I followed his advice. I got an 800.
This basic concept – that a student might benefit from taking some SAT Subject Tests as early as 10th grade – is one I passed on to both of my kids.