Fifteen-year-old Jenna Darnley, who was due to celebrate her 16th birthday next Monday and who was in her final year at the high school - was found hanged in the garden of her family home at The Hills, Grimsargh, last Friday by her mother Angela.
After leading a special assembly for year 11s on Tuesday after they returned from the bank holiday weekend, Headteacher Alan Lewis said the school community was "deeply saddened and bewildered" to hear of Jenna's sudden death.
Mr Lewis, who was assisted at the assembly by the Vicar of Longridge, the Rev David Anderson, said the school had been in touch with Jenna's family to offer their support and condolences, saying their thoughts were with them and all who knew her best at this very sad time.
He said: "At the age of 16, Jenna had her whole life ahead of her. Having already gained one GCSE and completed all her coursework requirements, she had every opportunity to perform well in the forthcoming final GCSE examinations. The fact that these opportunities cannot now be fulfilled is a tragedy.
"Jenna had a wide circle of friends within the year group who will miss her sense of humour and her loyalty. Those who taught Jenna and supported her progress through school are similarly shocked by her death."
On learning of the news on Friday, Mr Lewis said they immediately held an assembly for Jenna's year and after contacting families, a number of pupils were allowed to go home.
Jenna's parents, Angela, 42, and Bill, 39, and her 18-year-old sister Samii - who have been inundated with tributes to Jenna - have publically thanked everyone for their support, saying: "We are grateful to know how many people are thinking about Jenna and our family."
Not only have the family been surrounded by cards, flowers and letters of condolence, but the social networking sites Facebook and Bebo are full of tributes.
Describing Jenna as "happy and popular," the family say she returned home "cheerful and happy" on Thursday at 11pm after an evening out with friends.
But at 3.30am the following morning, Mrs Darnley, a team leader with Lancashire County Council, got up to have a drink and after noticing Jenna's bedroom door was open and she wasn't in her bed, went to look for her.
Police say they are not treating the death as suspicious, a post mortem was due to be held this week and a file has been passed to the coroner.