Britain's Home Office is launching an inquiry to establish how an adult asylum seeker was placed into a class of 15-year-olds at Stoke High School in Ipswich.
The man, who has been described to look as old as 30, spent six weeks at the high school in east England as a Year 11 student.
He is originally from the Middle East and faces being deported after an age assessment carried out by the local authority found him to be above 18, reported the BBC.
Asylum seekers who are below 18 when they enter Britain are entitled to a state education.
Known as Siavash, the asylum seeker was first captured on social media platform Snapchat with the message: "How's there a 30-year-old man in our maths class?"
The man is believed to be 1.85m tall, and pictures on his now-removed Facebook profile show him with a moustache and drinking beer, The Telegraph reported.
The British Home Office has not revealed Siavash's actual age.
According to The Telegraph, a Home Office spokesman said that age-disputed cases are a challenging area of work.
"In the absence of clear and credible documentary evidence, Home Office staff must rely on physical appearance and demeanour to make an initial assessment on whether a person claiming to be a child is under 18," the spokesman added.
Should the claimant be ascertained to be above the age of 18, their asylum claims will be treated as that of adults.
"If the application is unsuccessful, and appeal rights are exhausted, removal action will be pursued as appropriate," the Home Office spokesman said.
A spokesman for Stoke High School confirmed to the BBC that the man is no longer attending classes, but this incident has led to some parents removing their children from the school.
One parent, Ms Victoria Newby, told the BBC: "My girls will not be attending until I know for sure he's been removed."https://twitter.com/germanicgeorge/status/1058697375789826048