Student studying abroad

I do not have any specific recommendations, but for Spain I have used several of the primary booking sites (Hotels.com, Trivago, etc.) with very good luck. You might want to focus on areas easy for public transport, though for someone not familiar with travelling, it might be worth a taxi upon arrival.

Oviedo is a small city, not highly touristy, yet the hotel offer is quite decent.

I was going to Oviedo on a weekly basis for several months some years ago for a project with their regional savings bank and I used to stay at the hotel La Reconquista, it's very centrally located and the quality of their service is overall very high. I had some members of my team of consultants that also stayed at Hotel Ramiro I and a few others at Princesa Munia. Yet, this was invoiced to the client of course :).... if you're looking for something more "studenty" and also within budget, Residencia Juvenil Residencia Ramón Menéndez Pidal, a.k.a., REAJ (yeah, I know, long name!), Hostal La Peregrina or Chalet Villa Cecilia can probably fit the bill.

For info: "hostal" -which you'll find a few- has nothing to do with "hostel". A hostal is a type of establishment typical in Spain and it's like a basic hotel, simple and without frills, hence cheaper too. It's a good solution if you're just looking for a decent and clean place to crash. Also, know that the word for hostel in Spanish is "albergue".

In any case, check out this for more info: http://www.uniovi.es/en/vida/alojamiento

Finally, should he be interested in doing some tourism these two days:
https://www.turismoasturias.es/blog/-/blogs/las-10-mejores-cosas-que-ver-y-hacer-en-oviedo
http://www.turismoviedo.es/
http://www.oviedo.es/home

To expand your responses, I just saw today that there is a RS forum for student study abroad
https://community.ricksteves.com/travel-forum/student-travel