Customized environment for new users in XFCE

I come back to the community because I have a sad problem.

I just migrated from Xubuntu 14.04 to Xubuntu 16.04. The environment was personalized. That is to say, every time a student (I am in a high school) connected, he always had the same environment, namely this one:

https://framapic.org/IffPQ8CVHBC6/DHzTLS7j9LeN.jpg

I was using the /etc/skel folder to do this by copying my .config and .gconf into the /etc/skel folder. It worked perfectly and provided a beautiful desktop.

Problem, I can't reproduce this on my migrated workstation. As soon as a new user logs in, I get this:

https://framapic.org/AXn76wL0aTtD/Oz5DFyWvett0.jpg

And that gives me after that sad

https://framapic.org/j2zkHwizYQfg/6tQdC5zjVDqU.jpg

I have already done this on Mate 16.04 and Ubuntu 18.04 but now I'm drying out. Problem with XFCE?

Thank you for your help!