"It was an unbelievable match and it was an incredible statement about our kids and our club. It was a wonderful advert for the Academy and was a magnificent evening," Heighway told the official website.
"Our boys never give in and they kept fighting. They lifted themselves and boys who I didn't think had that quality did it. Southampton are a fabulous side, as good an under-18 team as I have seen.
"This match had so many twists and turns but the kids we have got are fantastic and I'm proud of them. They had tremendous courage to take the penalties at the end as seven of our team are under-17 players."