Thanks for your question. Unfortunately, after speaking with some other techs I can confirm that there isn't much we can do or suggest for a device that is locked behind a third party like a school administrator or an employer's IT department. Having his computer out in the open is definitely a help. If you haven't already done so I might recommend reaching out to his school to see if they might be open to installing accountability software on the device. They may also have their own filter that's being enforced on their end as well.
Thanks again for your question and I wish I had a more actionable solution for you Chance. Let us know if there is anything else we can assist with. Have a great rest of your day.