What are his subjects of interest/ gcses?
There are so many avenues in the built environment.
Planner, Architect, Landscape Architect, Land or Buildings Surveyor, Quantity Surveyor, Draftsman, Technician, Engineer, and then all the more niche specialities which follow from these broad topics - ecologist, horticulturalist, arboriculturalist, Tree Officer, LVIA specialist, interior designer, lighting engineer, consultant, project manager, BIM data coordinator, GIS Mapping, CDM coordinator etc. The list is endless.
And all the technologies which may appeal to a 17yo interested in computers - CAD technician, 3D renderer & modelling specialist, VR walk through visualisations etc.
Training in all these areas can be quite expensive if you do them individually so I wouldn't write off a degree course as it can give you a broad taster of all the different areas and access to explore them further.
If hes interested in the topic its unlikely he will be bored if he finds the right course which is broad enough and flexible enough.