Wales beat Italy 41-8 to finish in the top four of the tournament, and despite narrow losses to England (22-16), and France (10-7), in the semi-final and third place play-off, Lewis is happy with the development of his young charges.
"The purpose of playing international rugby at this level is to develop players for the future," said Lewis, who is also WRU National Academy Coaching Manager.
"I believe that at this age, the emphasis should be on challenging the opposition with the ball in hand and that's what we've been working on and what we asked of the players over the past week.
"In doing that, you will make mistakes but you could argue that we will have more skilful players who will be adept at whatever tactical approach coaches ask of them at Under 20 level and beyond."
Lewis believes this Under 18 group learned a vast amount from the past ten days. "It was an invaluable experience for these boys to play three competitive games in such a short amount of time.
"Against Italy, we scored some attractive, counter-attacking tries, against England we played some good football in periods, but they scored two tries from driving line-outs which made the difference. Against France, we failed to build the platform we wanted in the set-piece and when we did get some good possession, our basic skills let us know, but this is a good bunch of boys who are developing all the time. Their attitude on and off the field was impeccable.
Lewis believes the input the players received from Wales defence coach Shaun Edwards, who spent five days with the squad will hold them in good stead for the future.
"Shaun Edwards is one of, if not the best and most qualified defence coach in world rugby at the moment, and for him to have had such a direct influence on the players at this stage in their development is fantastic.
"They hung on his every word and his input gave our training sessions a new level of intensity and gave the players so much extra knowledge.
"We are hoping to further the development of this group with some game time against some southern hemisphere opposition in the summer months."