On your website I do find great and useful educational material that I would like to use. It is great stuff. But you have a copyright sign © on your website.
Now I do not know why you’ve put that copyright mark there. But now there is a problem because I am not allowed to use your beautiful material because you explicitly want to apply copyright.
So I cannot tell you whether I like using your material in my lessons, because I am not free to use it. Because that is what a copyright notice on your site stand for anyway?
Maybe you have good arguments as to why you want to retain copyright on your website, which is unfortunate.
Maybe you really want me and other teachers to use your educational materials. The copyright sign © an obstacle.
You could delete the copyright symbol and add a copyleft sign or creative commons. Then I can use your great materials, I would really appreciate it.
It is important that you make very clear which rights you want to apply, because if you just leave it copyright laws apply.