A Word About the ACT Test
The ACT is accepted in lieu of the SAT at many universities. It is a multiple-choice exam that measures English, Mathematics, Reading and - unlike the SAT - Sciences Reasoning. It’s given five times a year at several locations throughout the UK (but does not have as many testing centres as the SAT).
On each of the four tests you will receive a raw score. This will be converted to a scaled score from 1 to 36, and your final mark will be the average of your four scaled scores. Thus the highest you can get is a 36, which is equivalent to a 2400 on the SATs. The very best unis will be looking for a 32 or higher.
Most of the universities who accept the ACT will designate ‘with Writing’. The Writing score is reported separately and not averaged into the composite score.
Unlike SAT, you are not penalised for wrong answers on the ACT. This doesn't mean you should always rush through all the questions - make sure you give them the time they deserve - but it does mean that you should leave an answer for every question.
SAT or ACT?
With a few exceptions, US universities accept both these tests and treat them the same. In their current formats, the ACT is somewhat broader than the SAT Reasoning Test, covering the sciences as an add-on, and may be more in tune with your own education. Many schools, though, have experience of getting pupils through SATs but not the ACT, and SAT is the more common test for international students to take (probably due to broader selection of SAT testing centres).
Any requirement to sit SAT Subject Tests will apply regardless of whether you have taken the SAT Reasoning Test or ACT.