The Assessment test appointment need to make with welcome Centre. It take around one week to send the results to your school. Need to wait for they send the results before registration with school.
This is what I experienced last summer, not sure is update or not.
I think your grade will be determined by the assessment, I want my son to enter Grade 9 next year too but I am afraid he will get to a higher grade after the assessment. Or do they look at the year you were born to tell which grade you should be at?