Private Post BUT Public excerpt on Homepage

Hi everyone.

I’m building a website for a french school.

My problem : part of the website content will be private. Me and some other specified users will publish private posts (posts that only the 600 already-registred users will be abble to see).
But an excerpt of those posts (small photo+some text) shall be visible to any visitor in the Home page.
As soon as I set a post category to “Private” (using Role Scopper plugin), all excerpts of this post category, on the Home Page, also stop being displayed.

So what I’m trying to do is : “wheter or not a Post is set to private, force this excerpt to be displayed anyway”.

Any plugin / hooks / code to put in the loop or somewhere else ?

I’m using a theme (campus theme) that had been largely re-arranged (css-wise).

Thank you for your attention,

and sorry if bad english ??