What are your greatest priorities for your son? Let those guide your conversation. I know that with my own children my highest priorities are in character development, fitting in, and their overall happiness.
I want my children to love to learn, to have peers and real relationships with friends, and for them to be able to look back on their childhoods as happy ones. When searching for schools for each of them, we take these things into account heavily.
Let the school counselor know what it is that you really want for your child and that will be a perfect first step.