In the old days of the SAT, test takers feared bad test days because every score, good or bad, was included in the score report sent to colleges. No wonder we were all so stressed out! The policy of selective score reports, often referred to as Score Choice, ushered in by ACT felt far more civilized to everyone who recognized that no student deserved to be judged on his or her worst test. The College Board initially allowed selective score reporting only for Subject Tests but eventually expanded the option for the SAT as well.
The Score Choice option simply means that test takers may decide which test administration scores to send to colleges. Score Choice is the default option for ACT score reports but one that applicants must select when sending SAT score reports.
Obviously, the opportunity to designate which scores colleges see takes a lot of pressure off any specific day of testing. Just be aware that Score Choice applies only to score reports sent to colleges; the score reports students and their high schools receive include scores from all test dates. Also note that complete scores for each administration are sent, meaning you cannot only send, for example, the Math score from a given date.