Simplon Youth Hostel – this hostel is a short 5 minute walk to the city center, just outside of the canals. Simplon is not only a hostel, it’s also a concert venue and restaurant. It’s right next to Brouwerij de Prael, where you can try out craft beer brewed in Amsterdam.
Budd Gett Hostel – this hostel is conveniently located inside the city center. It’s also close to the train- and bus station. This hostel also arranges bookings for groups, so if you’re coming with your class or organization, this might be the right option for you.
Rebel Rebel hostel – this hostel is probably the coolest place to stay in town: you’ll sleep in old containers next to the old sugar factory, which is now a place used for events and festivals. It’s slightly outside of the city center, but there are bikes available for rent and a bus leaving close by. During winter, the hostel is unfortunately closed during the week, although it’s possible to stay here on Fridays and Saturdays.
Hotels are, like everywhere, quite expensive. Some cheaper options are the Stee in Stad, Mercure Hotel Groningen Martiniplaza and the Apollo Hotel. These options are outside of the city center, but there are good bus connections that will bring you to the city within 10 minutes.
If you’re coming with a group, your best option would probably be to stay in an Airbnb. The city has many of them and they are often cheaper than staying in hostels or hotels.