Wales now have to travel to Italy next weekend for their other qualifying game. France beat Italy 34-12 and Wales head coach Griff Rees says there is a lot for his side to work on.
"We were a bit naive at times and we need to take a look at ourselves before heading to Italy. It was a powerful French outfit and there are things we must tighten up on moving forward," admitted Rees.
The game got off to a flying start with French outside half Mathieu Guillomot-Bonnefon, crossing after only two minutes for the first of the game's seven tries. His half-back partner Clement Vernezoul added the conversion, but Wales were quick to respond.
It took Blues back row man Jenkins' men just two more minutes to conjure up the perfect reply with a try from vice captain Rhodri Williams. The Scarlets' scrum half saw his score improved by outside half Sam Davies and 20 minutes later Davies, son of Scarlets coach Nigel Davies, gave the home side the lead with a penalty.
At this stage Wales were creating well and holding onto the French pack, but penalty misses by centre Jordan Williams and Davies cost them the chance of increasing their lead.
The French then struck twice before the break with tries from hooker Christopher Tolofua and wing Joris Fusier to make it 10-17, but Blues centre Thomas Pascoe raced over for Wales' second try to give Davies the chance to level matters 17-17 at the break with his conversion kick.
France lost lock Stevie Cerqueira to the sin-bin just before the interval, but while they were down to 14 men they managed to plunder 10 points to put them on course for victory. Full back Quentin Pilet struck first with a penalty and then centre Thibault Regard ploughed over for his side's fourth try.
Pilet added the conversion and was on target seven minutes later when his skipper Alban Placine crossed for the fifth and final try. That meant 17 points without reply in 15 minutes at the start of the second period and Wales were very much on the back foot.
It didn't help the home cause when Scottish referee James Matthew issued Scarlets flanker Dan Thomas with a red card after 55 minutes for what seemed like a head butt. The French also finished with 14 men when scrum half Vernezoul was given a yellow card, but by then the result was not in any doubt.
Scorers: Wales U18: Tries: R Williams, T Pascoe; Cons: S Davies; Pen: S Davies. France U18: Tries: M Guillomot-Bonnefon, C Tolofua, J Fusier, T Regard, A Placine; Cons: Q Pilet 2, C Vernezoul; Pen: Q Pilet
Wales Under 18: Cory Allen (Blues / Glam Wands / Y Fro); Ryan J Evans (Ospreys / Bryncoch / Ystalyfera), Thomas Pascoe (Blues / Mountain Ash / Coleg Morgannwg), Jordan Williams (Scarlets / Llanelli / Coleg Sir Gar), Jack Randall (Scarlets / Ammanford / Amman Valley); Sam Davies (Ospreys / Gorseinon / Gowerton Comp), Rhodri Williams (Scarlets/ Llandovery / Amman Valley Comp); Nicky Smith (Ospreys / Gower College), Jack Dando (Blues / Penygraig / Coleg Morgannwg), Dan Suter (Ospreys / Tonmawr / Neath Port Talbot Coll), Jack Jones (Ospreys / Llandovery Coll), Rhodri Hughes (Ospreys / Hendy / Gwyr), Ellis Jenkins (Blues / Llantwit Fardre / Bryn Celynog. captain), Dan Thomas (Scarlets / Kidwelly / Bro Myrddin), Lewis Young (Blues/ Coleg Morgannwg).
Replacements Used: Evan Yardley (Ospreys / Bridgend Athletic / Brynteg), Thomas Davies (Blues / Ystrad Rhondda/ Ferndale Community School), Bradley Thyer (Blues / Ystrad Rhondda / Ferndale), Ieuan Jones (Dragons / Bargoed Youth), Josh Davies (Dragons / Llandovery Coll), Rhys Patchell (Blues/ CHSOB / Glantaf), Ryan E Evans Blues / Tonyrefail / Tonyrefail Comp)
Unused: Llywelyn Jones (Scarlets/ Haverfordwest / Thomas Picton),