DD (Harvard 2018) first took ACT and PSAT in sophomore year. It was all about practice and establishing a baseline. In the case of the PSAT, it was also to prepare for taking it again as a junior, since we always assumed she’d go to a NMF school (which she would have done if Harvard had not surprised us).
The ACT score was the eye-opener. When your sophomore earns a 30 composite, you start thinking about the future a little differently.