In the young Foxes' maiden outing of 2021, Ethan Fitzhugh located Pennant in space, in the 17th minute, to open the scoring for the home side on their debut outing at the Club's new HQ in Seagrave.
Tawanda Maswanhise set up Pennant to double his tally for Leicester's youngsters six minutes later, before Jon Rowe got the Canaries back into the game shortly afterwards.
However, City were relentless in their pursuit of goals and, in the 29th minute, Pennant completed his trio of strikes with a composed finish to make it 3-1 to the hosts.
Less than 60 seconds after the restart, it was four for the young Foxes, as Fitzhugh combined well with Will Russ to extended Leicester's lead, but Oscar Thorn's finish for Norwich gave the visitors hope at the interval.
It was 4-3, too, on 67 minutes as Abu Kamara dispatched a penalty beyond Arlo Doherty in Leicester's net, but the home side dug in to seal victory, aided by Rowe's 91st-minute red card for Norwich.
The result keeps City 13th in the U18 Premier League South division, but they are now level on points with Southampton and just three adrift of 11th-placed Reading.
Next up for the young Foxes is another home clash, with Reading, on Saturday 13 February (12pm GMT kick-off).
The details
City: Doherty; Abdullah, Obi, Ykefo, Cover; T. Pennant, Maswanhise (Wormleighton 87'), Marcal-Madivadua, Fitzhugh, Ewing (c) (K. Pennant 81'); Russ.
Subs not used: Chibueze, Kutshitnza, Butterfill.
Goals: T. Pennant (17', 24', 29') Fitzhugh (30').