I recently increased it from a 27 to a 31 when I took it to September after studying a good amount of time over the summer. I haven’t done any studying for the one in October because of HW and college apps. Is it possible to go up to a 33 if I just take a few science practice tests and maybe brush up on Math the night before? My subs are 34 English, 31 Math, 31 Reading, 27 Science. I feel like I may not benefit from studying from science and reading though because I feel like it is more of a “you got it or you don’t” type of thing.
I’d say you could increase your math 1-3 points if you work hard practicing (or maybe learning) and focusing on your problem areas. Some common problem areas for students in math would be questions involving the unit circle, trig functions, applying matrices to systems of equations, equations and theorems of circles and ellipses, coordinate geometry involving the use of formulas (e.g., the distance between two given points of a trapezoid on a graph - it may require you to form a right triangle that is not a part of the original shape to find the answer - which might require you to use the pythagorean theorem and then the distance formula), and maybe basic trig (law of sines, etc.).
As for science and reading, practice will help especially by taking practice tests. You should concentrate on comprehending information while reading quickly.
Even if you can work to get a minimal improvement in Math/Reading/Science it may get you to a 32 fairly easily which would open up more doors for merit scholarships - good luck.