Early College Admmission?

I took the SAT and I got a score of 1520: 480 Reading 510 Math and 530 Writing I want to enter a college(not community college) and take precalculus courses as a conditional/regular(!) student. However,I am merely 11 and when I asked Lehman College they replied only College Freshmen with their GPAs,Diplomas,and SAT/ACTs could enter.The GED,I checked is for >17 Years old.Is their any alternative way I can go to college,or earn something equivalent to a High School Diploma?