Should I retake the SAT or the ACT?

,

I've taken both the SAT and ACT, each with pretty average results. I took the SAT in March and scored 1090 (570 English & 520 Math). On the June ACT I scored a 23 composite (23E, 23M, 24R, & 23S).

I believe my weak points on the SAT were that I lacked the general rules and knowledge needed to score high. And on the ACT I had issues with the timing and pacing and a general lack of common ACT knowledge.

My goal for the SAT would be able to obtain a 1300+. And for the ACT to achieve a 27+. Which test should I focus on to achieve my target score?

My advice is to focus on the SAT based on what you've said here about your experiences with each test. Your issues with the SAT are associated with a lack of content knowledge, whereas your issues with the ACT are associated with both time pressure and lack of content knowledge. Since you're looking to raise each score approximately the same amount (relatively speaking), you should stick to the test that presents fewer overall problems for you.