The Ospreys and Scarlets Under 16s bagged victories in the WRU Age Grade Championship last night to put the pressure on previous leaders Blues North.
With the North not playing until Sunday, against North Wales, both regions made hay despite failing to pick up a bonus point.
Two victories in their opening three games became three in four for the Scarlets as tries from Gethin Hunter, Richard Bloomfield and Gareth Rees helped them to a 23-12 success over the Dragons at Narberth.
Meanwhile at Llandarcy, the Ospreys defeated Blues South 14-8 to secure a second win of the season.
Rhodri Lloyd gave the Dragons a 5-0 lead inside two minutes with his first try of the season and though Jordan Williams cut the lead with a penalty, Thomas Ashmead, with a try, and Josh Prosser's conversions helped the visitors into a 12-3 lead.
It was a different story after the interval with Hunter crossing for his fourth try of the campaign, after 53 minutes, and Williams adding a conversion and penalty for good measure.
However, it was not until the final quarter that the Scarlets pulled away with Bloomfield and Rees on the mark with tries.
Meanwhile at Llandarcy, a try from Cory Allen and penalty from James Morris kept the South in touch, but the Ospreys made the most of three yellow cards for the South and made sure of the victory spoils courtesy of three penalties from outside half Tom Carpenter and a try from centre Andrew Claypole.
High performance manager Gruff Rees said; "There were elements of the performance that need work, notably our finishing, but there was plenty of honest endeavour and we will take the win."
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.