My child had just passed CE exams A* and A's and is going to a academically selective Senior School.
Year 5 is too early for you or the school to decide- you can get ideas. At that time my child's prep school said that is was too early to be sure, but were mentioning the less academic schools and even suggested that at the particular academic school my child might struggle.
My child was just above average across the curriculum( very good at Art)- CAT test year 6 confirmed this as well! 105
By year 8 still undecided on Senior School- present school commented through out year 7 what good progress my child had made.
I decided at beginning of year 8 to opt for the most local not particularly selective school( gets great results considering not selective). My child's prep school supported my decision, but said that my child was more than capable of doing well in the academic selective school- after sitting the academic Senior schools own assessment , which was a CAT test( these results put my child in top 7% 127). This was also my child's first choice .
At the final moment we switched to the academic school, where 65/70% needed in CE, which my child comfortably got. Plus Art Scholarship at both schools.
For us Year 5 and 6 too early to have made a decision!
We needed year 7 to decide!
I suggest registering at 3 from non- selective to selective