Does the PSAT/ NMSF really reflect SAT and ACT? My son received a 660 reading , 580 math, and 230 writing and he has Aspergers that writing has always been a pro rom. Suggestions? BTW, it was taken second week of this year, his junior year.
To answer your main question, yes, the PSAT is very similar to the real SAT. The questions have the same format and content, so the only major difference is that the PSAT is a much shorter test. It does a pretty accurate job of predicting future scores on the SAT and ACT. Students typically improve the equivalent of 50-150 points from their PSAT scores to their SAT scores.
However, I'm a little confused about the scores you listed. The new version of the PSAT (which would have been the version of the test your son took last fall) doesn't have a separate Writing score. Reading and Writing are now combined into one score out of 760 points under the label "Evidence-Based Reading and Writing". The Math section is also out of 760 points, so the total possible number of points you can earn on the PSAT is 1520.
When you mention the Writing score, I think you might be referring to either his Writing and Language raw score out of 44 points or his Writing and Language scaled subscore out of 38 points. This article has a lot more information about what constitutes a good score on the PSAT for 2015 and may help you get more clarification on what the score report means.
This article, which provides a bunch of different strategies for improving SAT Writing scores, may also be useful for your son if he's worried about that aspect of the test. Performance on the Writing section will count towards your Evidence-Based Reading and Writing score on the real SAT even though it no longer has an independent section score.