I would ask the following 1)what lead him to the decision of going back to pursue his studies. I 2)What was his over all experience at your company 3)What he liked what he disliked. 4)What could you improve upon. 5)Ask about the quality of training and mentorship he received. 6)Ask about how he feels about your product or service. 7)Ask about his experience with co workers and management.

Depending on his position ensure that all his files are saved on a server for you to access after he goes. If he is working on any projects be sure to get a status update on where he is are and what needs to be done. As for his last day be sure to get any company issued property back.

Thanks ! That's a nice start.

He came to learn and I'd love to show him somehow all he learned. It's a lot and sometimes it's hard to explain it without perspective.

Ask him to create a detailed transition document for anyone else taking over his projects. List out any helpful tools, tricks, processes to get the job done.

Assuming that you need to back-fill this position, it might be worth asking him a professional referral. Who do you know that would be an ideal match for this role?

Finally, if he's amenable and there's good tonality-- a fair/favorable review on Glassdoor.

Ask if he would like to join again when he is done with his studies and if you can support him in any way during his endeavor.

Sure ! Our doors will be open and we want to make everything as easy as possible. We want him to leave with the best taste of the company.