This article is written for G Suite for Education Administrators.
Google Sheets has a huge database of functions. As you may not notice, some functions cross the line, allowing students to download data from the web. An example is IMAGE, a function working like inserting image by URL.
Another example is IMPORTFEED. It enables students to load and read online news feeds within their sheets.
This article explains how xFanatical Safe Doc can make functions inaccessible to students. If you have yet to install Safe Doc, apply for a 30 days trial.
What are the changes by Safe Doc?
Safe Doc allows you to blacklist certain functions that you considered inappropriate for your students, so these functions will no longer display in Google Sheets.
The follow screenshots demonstrate that the IMPORT* functions are removed.
Functions can be found and inserted by going to Insert > Function menu. The menu has a curated list of functions. Safe Doc removes the inappropriate functions so students cannot find them.
The same function list menu can be triggered by clicking the 
button in the toolbar. Safe Doc did the same as above.
Inserting functions can be done by clicking Help > Search the menus or shortcut Alt + /, followed by the keywords. Safe Doc removes the inappropriate functions from the search results.
When you start typing =IMPORT, Google Sheets will pops up an auto completion menu for you. This speeds up finding the correct function. Safe Doc filters the inappropriate functions from the list.
In the meantime, Google Sheets will also display an assistive function usage dialog. It includes function examples, a description and the format of each argument. Safe Doc blocks them for the blacklisted functions
How to Get Started?
Assume you have done Deploy Safe Doc To Your Students’ Chrome browsers and read Safe Doc Configuration.
Feed the policy BlockSheetFunctions with a list of function names to block. The function names are case-insensitive, so "image", "Image" and "IMAGE" are the same. For example, the following configuration blocks the IMPORTFEED and IMAGE functions.
"BlockSheetFunctions": {
"Value": ["IMPORTFEED", "IMAGE"]
}
Limitation
Although Safe Doc cuts the accessibility as if the inappropriate functions never exist, Safe Doc do not interrupt the functionality of these functions, per se. In another words, if students manually type a formula correctly, these functions behave as normal.
You may also like Disable Comment in Sheets or Remove Image Searching in Sheets.
Safe Doc
