Read-only access to other users within the same group

I was wondering if you could help please. I guess it is quite basic, but I’m a beginner on this.

I want to make a group, let’s name it students and add to it some users, let’s say John, Mary, Emily.
I want each user to have full control on their own home directory (that happens anyway, right) and read-only access to others.

How do you do this please in Ubuntu.