Blockly developed by Google is adopted by many educational projects:
https://developers.google.com/blockly/
Go to "Built with Blockly" which includes BBC MicroBit, MIT App Inventor, code.org, LEGO (3rd party), PBS, Minecraft (3rd party), etc.
https://developers.google.com/blockly/
Go to "Built with Blockly" which includes BBC MicroBit, MIT App Inventor, code.org, LEGO (3rd party), PBS, Minecraft (3rd party), etc.
(And this is someone who's spent most of his professional life working on visual programming systems.)