Congrats on the scores!
I don't have any specific info, but 6th grade isn't too young to take the ACTs, and 7th grade is a 'classic' time to take them to qualify for talent search. You can also buy a 'test prep' book for ACT and there will be 'practice tests' in there you can try at home.
With 33rd precentile for processing speed some practice and test-taking study seems like a good idea. There are many reasons for scoring low on speed - some can be improved with practice and other don't much improve. The only way to know is to try.
Best Wishes,
Grinity
