I'm not sure about all schools, but I applied to nursing school early action, and even though my grades and extracurricular activities were pretty good, I did not do amazing on the SAT (I am horrible at math). I did take the ACT though, and did fantastic (there are more topics and a wider range of material to be tested on). I was initially denied and placed into the regular applicant pool (which made me wait several months to find out for sure), but when I sent my ACT scores, I received an acceptance letter within a week. So they changed their mind and accepted me early action despite my low SAT but high ACT scores. I honestly recommend taking both so it shows a wider variety of your knowledge base (worked for me!). It does depend on where you are looking for school though, some are stricter about numbers than others.