What is a good SAT score for a current sophomore?

Good in what context?

Compared to the general 10th grade population, in your below/at/above average construct (if that means to 1/3s), probably <900, 900-1100, 1100+.

“Good” for an intention to apply to Caltech? A 1450+ probably indicates a path to a typical competitive score in Junior/Senior year testing.

Only on an inflated CC scale. 1470 is 97th percentile for juniors/seniors.