Judge Richard Foster told Hall: "Megan Peat will never experience the thrill and success of exam results, going on to higher education, or perhaps being a bridesmaid at a best friend's wedding or an 18th birthday party. Her life ended in your hands at 15 years old.
"Only you know why you did what you did that night and what the catalyst was for such a ferocious attack. It is clear you were jealous of her innocent friendships with others."
Hall relentlessly stabbed her 60 times in the head, neck and upper chest. Two knives, including a serrated bread knife, were found next to her body.
In a statement read outside court on behalf of Megan's family, Detective Inspector Richard Wall said: "Today we are satisfied that Andrew Hall has pleaded guilty to this offence. The day Megan died will be forever etched in our memories, it was the day our lives were torn apart."
It added: "Before her untimely death we were an ordinary family leading an ordinary life. Since that fateful day our world has changed beyond recognition.The pain of losing our beautiful daughter and the tragic and awful way she died will stay with us for the rest of our lives. Megan was loved so much and will be missed forever."