For my hub and spoke model, I am going to put myself in the shoes of a marketing manager for recruiting international students, agents and schools to your program. I would make my website or blog as my hub. I would most likely put a website or a blog in the middle, because I am in control of my website or blog and its content. A third party can not change the format like they can with Facebook or Twitter. As for my spokes, I would have a LinkedIn profile up as this may appeal to various professionals in the field (other schools, agents, recruiters). I would also have a Facebook site as a lot of students may have Facebook accounts and may feel comfortable using this form of social media. I would hope to gain fans and likes via Facebook which would bring them to my website or blog. I would also have YouTube as a spoke as I could put up videos (with other students consent) of past students, lessons and activities. Again, they would be directed to my blog or website. Twitter would be put as another spoke as a another way to gain followers and engagement. Past, current and prospective clientele could go back and forth on why they are looking for, why they like/dislike the program (past/current students) and what they are looking for. This was I could see what people are looking for and look to see what changes can be made.
I would use SlideShare another way to keep past and current clientele and attract potential clientele as it is very visual and you can say what you want to say short and to the point. This may appeal to an international audience whose first language is not English and does not have the ability or time to read a lot of text in English.
With these social media sites, I should be able to drive people to my website or blog. I would also be able to see what sites worked better than others and if I needed to use other social media sites, but to start with, I would use these ones.