To access classlink, go to classlink.mc-schools.net
It should be a page that looks like the one with a check below. If it's a page like the one with an X on it below, you're at the wrong site*.
The other problem people sometimes have logging in to Classlink is using the wrong username. Your Classlink username is your first.last --without @maryville-schools.org. The password is the same as your email password.
*You CAN log in at this site, you'll just need to be sure to fill inthe word Maryville as the optional code, otherwise Classlink won't know what school you're trying to log in to.