<p>Generally, American universities like to see a Math SATII (or in your case an A-level), even if the student isn’t planning to major in math or science. Students here tend to specialize later than European/British students, and a place like Yale is looking for academically (as well as in other senses) well-rounded individuals.</p>
<p>May is too late - decisions come out at the end of March, and the complete application has to be in well before that date. Your best bet is to e-mail Yale, or ask someone at your school who has helped other students applying to US universities to see how to approach your application process, which tests to take, etc.</p>