More than 350 pitched up at The Gnoll to see the two sides battle it out in an evenly balanced contest. But it was the visitors who left with a smile thanks to messrs Scarf and Gough.
Alex Wilkins with a try and a penalty from Nicky Roberts (Brynteg School and Pencoed Rugby Club) put the Ospreys in a decent position, but Scarf's first half try and a second, after the break, from Gough (Coed y Lan School and Ynysybwl Rugby Club) made sure of the points.
Christian Bala (Neath College and Merthyr Rugby Club) converted Scarf's score and Celyn Ashton of Treorchy Comprehensive School and Treorchy Rugby Club) improved Gough's conclusive try.
In the other game at under 18 level, the Newport Gwent Dragons lost out, 23-15, to Llanelli Scarlets at Abertillery Park.
A penalty from Phil Williams was not enough to earn Cardiff Blues South under 16s a second successive victory of the season at Stradey Park.
Williams knocked over his kick before the interval to keep the Blues South in touch, but the Scarlets were too strong and ran away with the spoils courtesy of two tries from Matthew Lemon and a third from Geraint Peachment.
Llanelli Scarlets 14 Cardiff Blues South 3
Neath Swansea Ospreys 14 Newport Gwent Dragons 13
Newport Gwent Dragons 15 Llanelli Scarlets 23
Neath Swansea Ospreys 8 Cardiff Blues 14