ACT High Composite/Low Writing, Selective schools

I am an international student doing the IB Diploma at an international school in China. I will be applying to Princeton and Stanford this year. I took the ACT with writing in April, June and September and respectively got 34 Composite/25 writing and 35 Composite/19 writing, 34Composite/(6/12Writing). These schools require ACT's writing test. I am worried that it will reflect poorly on how ready I am for college writing and also raise issues about the authenticity of my application essays. Should I retake the test (again)?

If I don't take the test again, which scores should I send to Princeton? (It allows score choice)

I am also considering Brown, which does not require but strongly recommends the writing test.

If you don't take the test again, I would recommend sending your first two ACTs (34 composite/25 writing and 35 composite/19 writing) to Princeton. As our article on what a good ACT Writing score is explains, a 6/12 on the new ACT Writing scale is roughly equivalent to a 19/36 on the September 2015-June 2016 ACT Writing scale, so submitting your third test wouldn't help you at all. This goes for Brown as well - "strongly recommended" means that you'll be at a disadvantage compared to other applicants if you don't submit a test with a high ACT Writing score and only submit your 35 composite/19 writing score (since there's no way to submit a test you with the essay without the essay score).

A 25/36 on ACT Writing is actually a 90th percentile score; while this score isn't as spectacular as a 35 composite score is, it's still a pretty decent writing score (especially considering the recent problems with ACT Writing scoring).

It's only worth taking the ACT a fourth time if you think that you can improve your Writing score through focused studying. Considering that students who are good writers have routinely reported getting in the low 20s on ACT Writing, I would say that a 25/36 is a fine ACT Writing score; most schools will place more weight on your composite score and admissions essay than on your ACT Writing score.