Warning: This report contains details of physical and sexual abuse and discussion of suicide.

Baobao's heart still races when she smells soil after morning rain.

It takes her back to early military drills behind locked gates - and the constant fear that marked every one of her days at Lizheng Quality Education School.

For six months, aged 14, she barely left the red and white building in a remote Chinese village where instructors tried to 'fix' young people whose families considered them rebellious or problematic.

Students who failed to comply were beaten so severely they could not sleep on their backs or sit down for days, she says.

Every single moment was agonising, says Baobao, now 19 and speaking under a pseudonym for fear of retribution.

She says she considered suicide, and knows other students who attempted it.

'Raped and beaten'

A BBC Eye investigation has uncovered multiple allegations of physical abuse in the school and others in the same network, and cases of young people being abducted and taken to the institutions.

Corporal punishment has been banned in China for decades, but we have collated testimony from 23 former students who say they were beaten or forced to do extreme amounts of exercise. One says she was raped, and two others, including Baobao, say they were sexually assaulted or harassed, all by instructors.

Undercover filming has exposed how staff pose as authorities to forcibly transfer young people to their institutions.

Thirteen students say they were abducted, with parental consent, by employees pretending to be police or officials.

The accounts - from interviews by the BBC World Service, statements gathered by activists, police reports, and state media - relate to five schools. These are part of a network of at least 10 schools, all of which have been run by - or have close links to - a military veteran called Li Zheng.

The centres are part of a booming industry promising anxious parents that military-style discipline will resolve concerns over young people's disobedience, internet addiction, teenage dating, and depression, as well as gender and sexual identity. Some parents even send over-18s, who are legally adults.

A series of abuse allegations have made headlines in China in recent years, both in Li Zheng schools and others.

In a few cases, arrests have been made or institutions shut down, but schools can be quick to reopen with different names or in different locations because the sector has been difficult to regulate. The BBC understands that Mr. Li was arrested earlier this year, but we have discovered his associates have recently opened a new school.

Companies and individuals involved in the network could either not be reached or declined to comment. The Chinese embassy in the UK told the BBC all educational institutions are required to comply with regulations.

'Deeply offensive' body search

Baobao says her mother took her to Lizheng Quality Education School in Hunan when she began skipping classes, triggering rows that made their already difficult relationship worse.

Her mother left while she was being shown around the school, she says, and she then realized she was not allowed to leave: They said if I behaved well, I might be able to get out.

Baobao initially tried to kick and punch the instructors, she says, but decided to comply when they tried to restrain her with her own shoelaces. Later, she was searched. She describes the way this was done as sexual assault. I found it deeply offensive… she touched all my sensitive areas.

She says her mother paid about 40,000 yuan ($5,700; £4,300) for six months at the institution, and she was not given any academic lessons. Few disciplinary schools offer these, and some that do charge extra for them.

The school is still operating, now known as Quality Education for Teenagers, with around 300 students, aged eight to 18.

Viral letters

Enxu's ordeal ended after a month. Her friends realized she was missing and contacted the police, who then located her and shared a video of her at the school. Her friend Wang Yuhang identified the school by asking in online groups about the green uniform she was wearing.

Enxu discreetly documented her experience in letters that were smuggled out and posted online. They went viral and as public pressure grew, the police intervened and she was allowed to leave.

Both Baobao and Enxu describe counselling sessions where little understanding was shown. Enxu's sessions were videoed for her parents, who she says had paid 65,800 yuan ($9,300, £7,000) for six months. Be a happy, healthy, positive boy. All right? she is urged. You're a boy, do what boys do… just be happy.

Both students wondered how their parents could have decided to subject them to the experience. Baobao managed to leave after feigning an eye problem. Her mother simply said let's turn the page, leaving her angry and confused, she recalls.

These schools are essentially scams, Baobao states. The prevailing educational ethos is one of violence begetting violence… the very concept is fundamentally flawed, she says, adding that they simply shouldn't exist.