Note: Requires access to add/modify code on your test site. Setup Log in as admin. Set TinyMCE as the main editor (this can be done from Site administration > Plugins > Text editors (move TinyMCE to the top of the list and ensure it's enabled). Set the theme to Boost . Clear site caches. Ensure there is a course created on the test site. Test 1 - Themes with no parent still work as expected Navigate to the course and select "Edit settings" in course administration. Scroll down to the description (Course summary). Expand the TinyMCE toolbar, then press the "<>" icon (Edit HTML source). Replace the contents of the editor with the following, then press "Update": <h1>Heading 1</h1> <h2>Heading 2</h2> <h3>Heading 3</h3> <h4>Heading 4</h4> <h5>Heading 5</h5> <p>Paragraph</p> CONFIRM all heading levels are easily readable, as per the screenshot: Press "Save and display", so the heading levels can be viewed again in later tests. Test 2 - Child themes can override editor scss Add the following to the bottom of <wwwroot>/theme/classic/config.php : $THEME->editor_scss = ['editor']; Copy the attached editor.scss file into the <wwwroot>/theme/classic/scss/ directory of your test site. Change the site's theme to Classic . Clear site caches. Return to the course's "Edit settings" page (or hard refresh if you still have it open). Scroll back down to the course summary. CONFIRM the headings appear in very small font (the last couple of heading levels will be unreadable). In preparation for the next test, remove the code added in step 1, and delete the editor.scss file you created. Test 3 - Child themes with no editor scss override use parent styles Undo the changes made in steps 1 and 2 of Test 2 above (ie remove the line from the config file, and delete the editor.scss file). Clear site caches (the theme should still be set to Classic ). Return to the course's "Edit settings" page (or hard refresh if you still have it open). Scroll back down to the course summary. CONFIRM all heading levels are now the same as they were for Boost, as per the screenshot at the end of Test 1. Test 4 - Atto still displaying as expected Re-enable Atto editor. Set the theme to Boost. Clear site caches. Return to the course's "Edit settings" page (or hard refresh if you still have it open). CONFIRM the Course summary heading levels appear correct, and make a note of their appearance (eg take a screenshot). Change the theme back to Classic and refresh the page. CONFIRM the Course summary heading levels appear the same as those shown in Boost.