Lagman claimed the boys' 12-under class after a very taxing championship match against Deo Talatayod, 7-5, 4-6, 6-2.
Lagman, the top-seeded netter in the division, managed to stay on course while Talatayod failed to hang on and bow down in the decided set.
The win gave Lagman a one game edge over Talatayod after five encounters.
Last week, Lagman was seen dominating the HeadPenn Group II Tournament at the Rizal Memorial Tennis Courts, a few days after he was named Headpenn's youngest product endorser.
Lagman now looks for a grandslam with the Copa de Manila starting next week.