Especially for educational usage, I am making this Music Education extension available for your MuseScore installation.
To use this extension, download the file below to your computer and use drag & drop from your file browser to MuseScore. It will install automatically. You may find this automatically switches you to one of the new workspaces, which you might not want, but you can switch workspaces at any time using the control at the bottom of the palettes window at left.
The Music Education extension includes two new workspaces that you can use as is or customize further.
The Music Education workspace is identical to the Advanced workspace that comes with MuseScore, except that it adds new palettes at the bottom of the palettes window.
This palette contains pictograms of the Kodály hand signs (do, re, mi, fa, sol, la, ti, do).
This palette contains text elements you can add to specific notes or rests in a score for comments in red (with or without yellow highlighting), a large red circled grade you can add to the title frame and then edit, and a yellow highlighter you can double-click to add to a selected range of your score. The highlighter will appear opaque blue when selected, so don't be alarmed, but once you move it into position and click elsewhere or press Esc to deselect it, it will be transparent yellow.
The Young Musicians workspace contains the same annotations palette as the Music Education workspace, but it also adapts user interface to be more "kid friendly" by customizing the font and icons sizes used and simplifying the toolbars and palettes.
The Music Education extension includes several templates grouped under the Education heading: