[jefrs]

What is the string length? - 3/4 scale would be about 19-in, about 5th fret on a full size one. I suspect it is a tenor rather than a student's 3/4 size (the age, the cutaway, the extended fb)

Try using good quality strings (expensive) but normal tension and tune up to GCFBbDG, it may want to go to ADGCEA. Make sure you get a good break angle at the saddle, the timber-hitch is not always the best knot to use because it lifts the string off the saddle. It should start to sing as you bring it up to its correct pitch. That should place it at normal tension, nylon strings exert much less tension than steel, even so high tension are a bit thicker. Action should be as low as possible, at shorter length and higher pitch the string excursion is less and the action can be lower.