Freda Hussain, head of Moat community college, donned ankle-length, green velvet robes and a flat-brimmed hat bearing an ostrich feather to claim the 1,000-year-old title.
For the next year she will not only be responsible for her 1,050 pupils and 150 school staff but also will be looking after law and order throughout Leicestershire.
Mrs Hussain was nominated for her new post by Anthony Wessel, a former high sheriff, and is thrilled by the one-year appointment.
But she has promised not to let it affect her day job: "I am a teaching head and there is no way that my role at Moat will decrease - nor would I want it to.
"I have two deputies in my role as high sheriff, in whom I have full confidence. But my prime responsibility will be to discharge my duties as principal of the school."
Being high sheriff can prove a costly affair. There is no allowance, not even expenses, and although Mrs Hussain will not disclose the cost of her smart new uniform, she admits it was "expensive". Mrs Hussain, who is married to a university lecturer and has a daugther who teaches, was given three years notice of her appointment.
She has been training herself in the art of being high sheriff and said:
"Hopefully I am well versed in what will be required."
Mrs Hussain, who was awarded an MBE last year for fostering understanding among Leicester's diverse ethnic communities, is determined to put education at the forefront of her new role.
"This is an honour that I hope will reverberate in a positive way throughout the county," she said. "I want to use my year in office to involve education in every way possible with the duties of a high sheriff."
Those duties range from supervising the opening of the Crown court to making sure there is a ritual posy of flowers for the visiting judge, and organising a race night and civic reception for more than 300 dignitaries.
"I believe everyone from the police to local businesses has something to teach young people," said Mrs Hussain.
"I want to use my year to try to bring organisations and people together, so that we can all give something positive back to the young people of this multi-cultural city."