No, student items must be approved by the teacher before they are published and shared with parents. When students add new items, they go into an approval queue for the teacher. Teachers then go through the unapproved items, delete any inappropriate items or re-assign authorship, and then tap Approve All to approve all the remaining items. Only after items are approved by the teacher, are they added to journals and shared with parents. You are always in control over the content published in your class.
Note - items that are added when logged into the Class app as a teacher (“I’m a Teacher” > email address and password login) are automatically approved.