He was described as a “remarkable young man” by his headteacher at the prestigious £10,000-a-year Gads Hill School in Higham, Kent, set in the former home of Charles Dickens.
Charlie was found dead by his parents on March 8 at their home in Watling Street, Cobham, Kent.
The coroner ruled that Charlie took his own life.
Hours before his death police were called to the family's home between 6pm and 7pm to reports of text messages of a sexual nature being sent to a girl, the inquest at Gravesend's Old Town Hall heard.
Det Sgt Lee Neiles, of Kent Police, told the inquest: "She wanted them to stop.
"Nick (Charlie's father) gave him words of advice and they went to KFC in Valley Drive in Gravesend and Nick said he (Charlie) had to be careful about contacting young girls.
"They had a KFC but Charlie seemed withdrawn."
They returned home and Charlie went to his bedroom.
Around 10pm his mother Julia came back from an evening with her friends in Bluewater to hear about the complaints made against Charlie.
She told her son off and confiscated his mobile phone. Around 30 minutes later while Mr and Mrs Booth were downstairs they heard a loud bang.
Det Sgt Neiles said: "They went to his bedroom and Julia saw a light coming from the spare room and found him on the floor in the corridor.
"She said she saw him on his side and he was clearly dead."
Kent Police and South East Coast Ambulance were called at 10.32pm and Charlie was pronounced dead at the scene.
Det Sgt Neiles told the court Charlie shot himself with the intention to commit suicide.
He said: "This is on the basis Charlie had a shotgun and knew the power it possessed and Charlie was extremely worried about getting into trouble regarding the text messages.
"The note in his jogging bottoms appears to be a suicide note."
Paying tribute to Charlie, Det Sgt Neiles said: "Charlie was a popular boy who enjoyed playing rugby and hockey.
"He was due to go on a trip [to Alaska in July] and had raised £3,000 by organising quiz nights and working.
"He had been accepted into King's Rochester. He had everything to live for."
Shooting champion Charlie received a gun as a present for his 15th birthday and was a member of Gad's Combined Cadet Forces (CCF).
Det Sgt Neiles said: "Everybody chipped into to buy him the gun and he was over the moon.
"He was a totally responsible and was trusted by people to handle a gun. He used to go out shooting with his dad.
"He was a typical country boy. He never drank, apart from the occasional cider with his dad."
Passing verdict, North Kent Coroner Roger Hatch said: "I have no alternative to record other than Charlie Booth took his own life. I express my sympathies to the family."
A tribute issued by his father Nick, 52, mother Julia, 48, and sister Harriet, 12, at the time of his death said: "As a son he was a very loving boy that had a very supportive family, not just his parents, but his aunts, uncles, cousins and grandparents.
"He thought the world of them and we all thought the world of him.
"He was just a typical country boy that enjoyed school life, loved outdoor pursuits and he fully embraced the country lifestyle.
"Charlie was one in a million, very popular and well-liked, and was quite simply our beautiful boy."
Gad's Hill headmaster David Craggs added: "Charlie was a remarkable young man, who had such a bright future ahead of him.
"Charlie was a friendly, enthusiastic, mature and self-confident student with so much to live for - attributes that make this tragedy even more difficult to comprehend.
"Charlie's legacy will live on in our fond memories of him and in the eternal love of his family."