^ starting to practice before the October PSAT is good if a top score can reasonably be expected (don’t overload and don’t stress out your child if s/he scores around the 50th percentile - s/he won’t become top 1% in a year, focus on raising scores but not by PSAT time). The SAT subjects can be taken at the end of the 11 grade school year (May or June, whichever is close to the end of school but leaves some time “free” to review), and one SAT Reasoning OR ACT needs to be taken before the end of the year. Then the Spring subject test you did less well in and another subject test can be taken in the Fall, as well as another Reasoning test or ACT.
(Some colleges only ask for ACT or SAT Reasoning+subjects, but this testing regimen covers all possibilities).