Seth Walsh died nine days after hanging himself in his garden on September 28th. His family said he had endured years of harassment and abuse at school for being gay.
Last week, his mother Wendy accused the Tehachapi school district of ignoring her pleas to tackle the bullying.
She said his grades had fallen and that some teachers had even joined in the harassment.
Yesterday, a spokesman for Education Secretary Arne Duncan confirmed that federal education officials were investigating how the school district dealt with the issue.
Mrs Walsh said she contacted Department of Education investigators while her son lay in hospital in a coma before he died.
She said they spent two days in Tehachapi last week, interviewing teachers, administrators and students.
In October, the Education Department’s civil rights division told school districts that they must take steps to stamp out anti-gay bullying.
According to Associated Press, the department has the power to investigate school districts where bullying is said to be so severe, it has resulted in a “hostile environment” for students who are, or are thought to be, LGBT.
Mrs Walsh is being supported by the American Civil Liberties Union, which last week sent a letter to the school district on her behalf asking it to prevent another tragedy.
The ACLU says that at least 11 US LGBT teenagers have killed themselves after suffering bullying in the last few months.