It won’t be a problem that multiple participants take the the experiment at the same time: all the scripts and resources start loading at the beginning of the experiment (when the link is open) and then everything is executed locally, on the participant’s machine. Only when the end of the experiment is reached is the server contacted again, to submit the responses. The two first columns in the results file will report a timestamp for when the responses were received and a sequence of letters and digits unique to the browser and IP of the participant. It is quite unlikely that two students would submit at the exact same millisecond, but even if so, if each student uses a different device, the second column should report a different value anyway
Jeremy