How Soon Can You Take the SAT, PSAT, ACT, and Subject SATS in High School and have them count?

I wanted to get ready for college as soon as possible since I found out today that I was not offered a spot at the private school I applied to. I know that you can take the PSAT as a sopre, but it doesn't count. I was wondering when you could take them and have them count. Knowing when they don't count could also be helpful. Thanks.