The Blues South were beaten 31-7 at Llandarcy whilst the North went down 25-11 at Merthyr.
The under 18s, understandably buoyed by their outstanding pre season, were always in control of a game that saw the hosts lose Haydn Baines to a yellow card before half time.
James Russell kept the Scarlets in touch with a couple of penalties, but the Blues made sure of victory thanks to tries from outside half Joseph Griffin and blindside Callum Thomas.
Griffin, who was outstanding throughout, added a conversion and two penalties to secure an important away success with team manager Sophie Bennett pleased that the side were able to build on their summer success.
"We were delighted with what happened over the summer but it was important to take that into the season. I think we have done that, now it's important that we build on our performance in the next round of games.".
At Landarcy, the South under 16s were put to the sword by a decent looking Ospreys side who finished with a bonus point to boot.
Matthew Jenkins and Evan Yadley crossed for the Ospreys in the first half with Ben Roberts and Sean Macdonell-Roberts adding further tries after the interval.
Outside half Sam Davies kicked four conversions and a penalty to complete the rout with Jordan Phillips crossing for the South and Gareth Thompson adding a conversion.
Meanwhile a try and two penalties from Callum Phillips was not enough to prevent the North from slipping to defeat at the hands of the Dragons.
Locked together 6-6 at half time, it was the Dragons who took control after the interval with tries from Hallam Amos, Jack Dixon and Dominic Franchi.
Ethan Davies added to his two first half kicks with a second half conversion of Dixon's try whilst Niall Martin improved Franchi's score late on..