Natasha Paton died in the crash near Biggar in South Lanarkshire
The head teacher of a South Lanarkshire school has paid tribute to the 17-year-old pupil who died in a bus crash in "horrendous" weather conditions.
Natasha Paton was killed when a coach carrying pupils to a theme park plunged off a bridge on the A73 near Biggar early on Wednesday.
Mark Sherry described her as a "popular pupil and friend" and said she "always had a smile for everyone".
He said Wednesday had been "a very sad day" for Lanark Grammar.
Investigations are continuing to establish why the bus crashed near the village of Wiston while it was taking 39 sixth-year pupils and five members of staff to Alton Towers in Staffordshire.
Three others injured in the crash remain in hospital.
South Lanarkshire Council has confirmed that the coach involved was fitted with seat belts, to comply with the law.
Mr Sherry read a brief statement at the school but did not answer questions about why the trip was allowed to go ahead.
He said the 17-year-old schoolgirl had been looking forward to the outing to Alton Towers.
"Natasha was a very popular pupil and friend who had high hopes of passing her exams and possibly going on to further education," he added.
Head teacher's tribute to crash victim
"She was a young person with a lovely nature towards everyone in school.
"She was a lively personality with a wide circle of friends who enjoyed her sense of humour."
Pupils at Lanark Grammar were being offered counselling from education and social work staff.
The school was not open for lessons on Thursday but about 200 pupils gathered for a service dedicated to their classmate.
Mr Sherry said: "It is a very sad day for all of us at Lanark Grammar, particularly for Natasha's close friends and classmates, as well as her teachers.
"I would like everyone affected by this tragic event to know that they will continue to be in our thoughts and prayers at this time."
School chaplain, the Reverend Sarah Ross, said: "The support that the children have shown for each other has been really immense.
"The sense of community in Lanark Grammar has really come to the fore.
Friends of the schoolgirl laid flowers at Lanark Grammar
"Just being together and being able to see that other people feel the same way as they do has proven to be very important."
Police believe the coach lost control as it approached a tight bend and fell 10ft into the river, crashing through the bridge wall.
Miss Paton is thought to have been thrown from the vehicle then become trapped under it.
In a statement released through police, her parents said they were devastated at the loss of their "beloved daughter".
They described her as a "typical teenager" and said she would be missed by everyone who knew her.
Pupils and parents laid flowers at the entrance to Lanark Grammar and tributes from friends have also been posted on the 17-year-old's Bebo page.
Speaking on BBC Radio's Good Morning Scotland programme, the general secretary of the Head Teachers Union in Scotland, Ken Cunningham, said organising school outings placed a huge burden on staff.
He said excursions were immensely beneficial for youngsters, but entailed a great deal of work, preparation and risk assessments.
"No matter how much preparation goes into these trips, and there is a lot of it, you never know what can go wrong, " he said.
"What I do know is that other schools left to go on similar outings in these conditions yesterday and this is the one that ended in tragedy.
"There are judgements taken by professionals and you have to rely on these judgements. There some things you just can't foresee."
South Lanarkshire Council said it was helping Strathclyde Police with its investigation into the crash.
A spokeswoman said the police had asked the local authority not to discuss the reasons for travel or the circumstances surrounding the crash.
The school is now closed for the Easter holiday and the spokeswoman added that the council would not be making any further statements regarding the incident.