SAT diagnostic test score?

It's an average score, but I am not sure what diagnostic test you took. You can improve by studying the SAT. Use the College Boards Official test prep book and do all of the tests. You will take the PSAT this October. You're score report will include your projected SAT scores. Most people take the SAT in the Spring of Junior Year and the fall of Senior year. Some people take it three times, but more than three is overkill. 1660 is good enough to get into many colleges but not the selective schools. You need to shoot for 2100 for those, and not less than an 1800. For the Ivy's you should be scoring as close to 2400 as possible.