Although you initially own the copyright for your works, copyright can be transferred.
Before you sign a publication agreement, be sure to read over the agreement to know what rights you are giving up. Be careful about giving up rights -- for example, if you transfer your rights you may lose the ability to post your work in the LMS for students to use.
Make sure you do not give up rights you want to keep, and try to limit the grant to what the publisher needs to publish. You can negotiate with the publisher regarding the rights you give up / future use you can make of a work. You may have to evaluate whether you want to give up the rights required by the publisher in order to have the work published.
After you sign the publication agreement, keep a copy for your records. If you want to use the work in the future (or give someone else the right to use your work), you will need to know what rights you retained and what rights you gave to the publisher.
You can also look at the journal's website to see if it provides information regarding what rights authors who publish in the journal retain.
An additional resource for finding journal copyright policies is to look at the Open Policy Finder (formerly SHERPA/ROMEO) website linked below. You can search by journal to see if a journal's policies are listed.