Chasam Sofer sounds like a good choice, but by age 17 maybe he is looking for a post high school yeshiva? Although I think they go a few years past high school. My brothers were there for elementary school and left for high school because they did need more of a demanding high school so it sounds good for your son.
It is sad that yeshivas gear themselves for the “top” bachurim and leave the weaker students to the dogs. I remember in high school I felt that a lot of teachers aimed their lessons at the top 10% of the class and the rest of us would have to try to keep up.
I feel that teachers should gear their lessons to the average students. The weak students should be provided with modification if necessary and the gifted students could be given extra to be stimulated. It sounds simpler than it is. I know it’s not. But who says the weaker students aren’t worth enough to spend extra time to make it work for everyone?