Hello Nicole @Anonymous
Welcome to the AutoCAD Web App forum.
Can you clarify which browser the student is using? Since I can not reproduce the issue on my side and it only happens for one student, the browser might be the issue. Furthermore the help does not mention something about disabling the dynamic input (See: Dynamic Input and Shortcut Menus)
Supported is actually: 64-bit Google Chrome, 64-bit Mozilla Firefox, and 64-bit new Microsoft Edge (Chromium based) on Windows or Mac (See: Supported Browsers and System Requirements)
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Best regards,
Thomas
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Thomas Stühle
Technical Support Specialist