Joanne Watson, pictured, died on Friday after collapsing during a PE lesson at Kettering Science Academy.

Writing on her daughter's Facebook profile, Stacey Watson said: "My beautiful girl, why did you have to leave us so soon? My beautiful angel, never leave my side. I love you baby.

"Every day with you made me smile so much. I hope you will be watching over us as I know I'll be looking up at you just to see your beautiful face once more.

"I love you so much. I can't believe you have gone. Sleep well my little princess."

Peter Simpson, executive principal of Kettering Science Academy, said the school was in shock.

An assembly was held to allow pupils and staff to pay their respects to Joanne, who Mr Simpson described as a 'lively, vivacious, bright girl who loved PE'.

Mr Simpson said: "There were moments of silent prayer and contemplation that were very profound.

"I think the students are behaving in a very mature, balanced and appropriate way."

Joanne's classmates and members of staff have been offered couselling by the school.

A book of condolences has been started and every pupil will have the chance to leave comments.

Joanne's step-sister Daniella Bryan, 14, of Wellingborough, said: "She was a fun little bubbly girl. Anything that got chucked at her she could handle.

"At the moment I'm thinking of her big cheesy smile. She had a smile that you couldn't forget."

Her step-brother Chris Bryan, 16, said: "I miss her. She meant the world to me.

"She was a beautiful little girl."

More than 550 people have already joined two Facebook pages set up in
Joanne's memory since Friday.

Family and friends have left scores of tributes on Joanne's own Facebook page.

Sienna Barrett wrote: "Sweet dreams gorgeous. You lit a fire in everyone's heart and the truth is the flame will never go out."

Cassie Abigail Neale added on the site: "You were a girl full off talents and my best friend. Forever is the time you'll be with me."

Georgie Trevor said: "I miss you princess. RIP. I love you."

Paris Bliss wrote: "RIP Joanne. You were such an amazing person and you are going to be a beautiful angel."

Chloë Ingram wrote: "Joanne, love you so much. I'm never ever, ever going forget you. School won't be the same without you."

Alisha Cope wrote: "Joanne, you know how we always used to say best friends till the end? Well, the end's never going to come because you will always be with me no matter what. Sweet dreams."

The cause of Joanne's death is not yet known.