Harrison joined over the summer following a long and successful stint in the same position at West Bromwich Albion, where he helped them to become one of the best in England for developing young stars.
Smith said: "I was involved in the recruitment process for Mark, along with Jesus Garcia Pitarch, Jeremy Oliver and Christian Purslow.
"We wanted the best Academy Head that could make ours the most progressive in the area.
"They knew how to produce players there. Now, I think Mark will take over here and push us forward.
"We want to be the best Academy in the area, and even the country. That's got to be the aim and the ambition.
"We also have Richard Beale in now with the U18s – another established coach who is very good at his job. I've known him for a long time.
"And we have George Boateng, who understands the club and knows what's required. He was a top professional who played a lot of games at the highest level."