How does high school diploma affect college admission.

It just means you graduated highschool.... If you have it..great if you dont- you can still go to college in some places but you most likely wont be accepted. Most schools require at least the minimum a GED certificate because it is considered a high school equivalent, but a few schools bar applications from students with GED certificates. If you dont have either you're possibly looking at a community college but sometimes they require it too..

It would help if you had a diploma or equivalent to be considered.