Concerns about the relationship between a teenager and her maths teacher were already being investigated before the pair apparently ran away together to France, the local authority has confirmed.
The parents of 15-year-old Megan Stammers have made an emotional appeal for her to get in contact with them, after she caught a ferry to the continent last week with 30-year-old Jeremy Forrest.
It has emerged that concerns were expressed to another teacher about their relationship, following a school trip to Los Angeles in February.
A friend from Bishop Bell Church of England School in Eastbourne, East Sussex, said another classmate had raised the issue after seeing the pair holding hands on the return flight.
The 15-year-old friend told the Daily Mail: "They would always text each other. He would send her messages saying things like 'I miss you' and 'I can't wait to hug you'.
"We are really angry the school did not do enough to protect Megan. And now no one knows where she is or if she's coming back.
"I don't know how it all started with Mr Forrest but to begin with she was really excited about it.
"She would tweet about being in love and show us his texts. But after it was reported she stopped and then deleted her Twitter account. She never spoke about it after that and she didn't tell any of us that she was leaving. She probably knew we would stop her."
An East Sussex County Council spokesman said: "Because the investigations are ongoing we are not going to comment in detail, however the school and the county council had been addressing and investigating concerns that had been raised, in line with procedure, when this happened
"That investigation will continue and we will decide what action to take."
A senior police officer has also disclosed that a message was sent to one of Megan's friends, saying she was in France, but it did not come from her phone.
Chief Inspector Jason Tingley of Sussex police said: "I can't give a specific time or date but we know there was a message passed to one of her good friends to say she had arrived safely in France.
"I can't say that message was from her but we believe it was. That gives us some comfort that she has arrived safely and she is in France. That's our last contact."
Last Thursday, Megan asked her mother, Danielle Wilson, whether she could stay overnight at a friend's house. Her mother said she agreed, gave her dinner money for school the following day – and Megan left.
But the following morning, her mother received a text message from her school, where Forrest teaches, saying she had failed to attend classes.
Checks were made to see whether the friend she claimed to be sleeping over with was at school, and when it was confirmed that she was, alarm bells rang.
Her family revealed that Megan had been receiving extra-curricular maths lessons since before the summer. But they did not suspect any relationship between her and Forrest, a married amateur musician, who lives in Ringmer, near Lewes.
Wilson said: "There were a couple of subjects that she was struggling with and she was going to after-school extra tuition. One of them was maths, but that didn't alert me because I knew it wasn't one of her favourite subjects. I knew she struggled with it.
"For her to say that she was going to attend those classes was completely natural. Why would you think anything of it? She was not only attending maths but also science."
Her stepfather, Martin Stammers, said Megan had never expressed any wish to visit France. He said: "She loves LA, she loves New York, but she has never mentioned Europe."
Her mother added: "The only thing she would say was that she wanted to be famous."
Stammers said he was "aware" of Forrest but refused to go into further detail, saying: "It's about Megan and getting Megan back."
They said it was completely out of character for her to disappear but police said they believed she had travelled willingly.
At the news conference at Sussex police headquarters in Lewes, it emerged that the pair travelled out on a ferry on Thursday and were due to return to the UK on Sunday, but did not use their tickets.
"She is always in at 7pm, she is not one of these kids to roam the streets, she doesn't go out drinking or anything like that. She doesn't like the dark so she had never been out after dark," Wilson said.
She added: "It is completely out of character, this is not her, she is not like this."
Stammers told how Megan sent him a text message last Tuesday asking to meet him. He arranged to meet her on Saturday but she did not keep the date as she and Forrest were believed to have already left for France.
"We had a date on Saturday, we didn't make it. Babes, that offer's still there sweetheart," he said.
"[I] just want you to come home safe and well, babes please."
Describing her as "everything you would want in a daughter", he added: "We are a family unit working together, strength is coming from within all of us, as a family, our close friends [are] striving so hard.
"I would like to thank the people supporting us out there on the social networks, Twitter, Facebook. Please keep posting, keep tweeting, please keep retweeting."
Appeals for help in tracing Megan have continued to be posted on Twitter and Facebook, including by her sister Brooke.
She tweeted: "Keeping hope that we'll have good news soon. Need our meg home safe and sound #keepfaith #findmeganstammers."
East Sussex county council and Bishop Bell school said they were investigating and working closely with the police.
Terry Boatwright, the school's executive headteacher, said: "The whole school community is deeply concerned for Megan and shocked by what has happened.
"The thoughts and prayers of us all are with Megan and her family at this time.
"We would urge her to get in touch with her family to let them know she is okay and we would echo the police's call for anyone with information to contact them."
On a blog apparently written by Forrest under his music stage name Jeremy Ayre, he writes about a "moral dilemma" in a posting four months ago headed "You hit me just like heroin".
Posted on 19 May, it says: "The last two weeks have been pretty intense, in both a good and a bad way!!!
It continues: "About a week ago I had a bit of a moral dilemma to deal with, both internally and externally. And the over-riding question it left me with was this: 'How do we, and how should we, define what is right or wrong, acceptable or unacceptable???'
"I came to a few different conclusions, mainly that actually we get a lot of things wrong, but at the end of the day I was satisfied that if you can look at yourself in the mirror and know that, under all the front, that you are a good person, that should have faith in your own judgment.
"That's some philosophical gold for you there!!!"
Forrest is 6ft, slim with fuzzy facial hair and mousy brown hair. He wears square glasses, dresses casually and has a black star tattoo on his upper left arm.
Interpol, the UK Border Agency, the British embassy in France and the French authorities were working to help trace Megan.
Anyone with information is asked to call Sussex police on 101 (in the UK), quoting Operation Oakwood.
A dedicated telephone number and text number that can be used from abroad have been set up. They are 00441273 475432 or text +447786208090.
