I heard that for St. Andrews and other Scottish universities, international students have to apply in their junior year. Is this true? If not, does anyone know when? And what to do if one hasn’t taken any SAT IIs by spring of junior year? Thanks!
Not true. You apply in the autumn of your senior year.
Thank god! Thanks for the info 
I’m not sure about other schools, but St Andrews does rolling admissions. If you have the test scores you want, apply sooner rather than later. I didn’t submit my SAT scores to St A’s, just my AP and ACT. Take the SAT or ACT as soon as possible though; your test scores matter significantly more than your GPA for UK schools.
Good luck!!
Most UK schools are rolling but they close in January.
Check the UCAS deadline for more info. If you’re applying Oxbridge or medicine you’ll have to submit in October.
Please look at St Andrews website. It is all on there. I would have thought you would have done that first.