We did the Sutton mocks. It gives a hint. He was actually in the top 50. But I still wasn’t sure how he’d actually do on the day(s).
He got a place at Tiffin, and various scholarships to various indies. So maybe it gives more than a hint! However, tests throw curve balls. He didn’t pass the second round of Wilson’s (1 mark off the cut off!).
I think your son being in the top 15% is a good sign. He will probably pass to one of the grammars, but it’s not a done deal. But then, it never is!
In your shoes, I would certainly apply to one (or two) of the “top tier” schools, but also go for other great schools that ARE easier (but not “easy”!) to get into: eg whitgift, dulwich.
I wouldn’t bother with the shiny (nice facilities etc) indies that aren’t academic.
In the end you want a school that your child flourishes at, not one they struggle in. But equally, you want a school that helps your academic son to fly (or we did. He absolutely coasted at primary!)
However, you know your son! One test doesn’t show the whole picture. Eg my kid didn’t pass for Wilson’s! But he got into Tiffin.
Also think about your child. His personality. At the top tier schools, and I assume the SS grammars, they work FAST. just yesterday, he (year 8) had a list of about 40 French words to learn, biology homework, maths that I didn’t understand, and an after school football match. If he were struggling, or didn’t enjoy learning, he would be very miserable.