Comments can be enabled or disabled on a per post basis, and post before the settings change will have them enabled.

To change this in SchoolPress/WordPress you need to navigate to:

To edit a Post or Page individually:
  1. Navigate to Posts or Pages
  2. Click Edit on the Post or Page you would like to disable comments on
  3. Click Screen Options at the top right corner of the screen
User-added image
  1. Select Discussion
User-added image
  1. Scroll down the page to the Discussion area and unmark Allow Comments
User-added image
  1. Click Update

To Edit Posts or Pages in Bulk:
  1. Navigate to Posts or Pages
  2. Mark the checkbox next to the Title Header to select all (or select the posts or pages you would like to edit)
  3. Under Bulk Actions, select Edit
  4. Click Apply
  5. For Comments, select Do Not Allow
  6. Click Update
User-added image