The phrase "has been an apprentice at" is correct and usable in written English.
It is used to describe a person's past experience or past role in a company. For example, "He has been an apprentice at a local bakery for the past two years."
Sean Egan, an engraver, said he had been an apprentice at the factory for a decade, from age 15 to 25, before he was allowed to wield his tools unsupervised.
He had been an apprentice at Swansea City football club before being commissioned into 1st Battalion, The Royal Welsh Royall Welch Fusiliers).
As someone who had been an apprentice tailor at the age of 14 (before turning to psychology), he was a practical man, but he had no expertise in entrepreneurship.
Montanna Carty, 17, has been a health and social care apprentice at aVida since October 2014.
The Apprentice has been a runaway hit for NBC, a division of General Electric.
9 P.M. (NBC) THE APPRENTICE -- It has been a busy season for Donald Trump's would-be apprentices.
A Lincolnshire man who had been a punter and an apprentice at Swan and Edgar's he risked offering Princess Metternich a couple of dresses at £12 a time and won the custom of the Empress Eugénie.
35 There must have been a benefit to masters as well as parish officials, however, or they would not have accepted parish apprentices (although masters could be forced to take apprentices this seems to have been rare in practice).
Firoz Patel, 23, from East Ham, has been working as an apprentice steel fixer at Crossrail for the past nine months, for 50 hours a week, meaning he fits the steel bars and mesh which reinforces concrete structures.
Lower's right hand, Christina Kelso, who has been apprenticing with him since she tasted his grapefruit at a farmers' market four and a half years ago, is a raw vegan who loves to make a salad of dates, apples and pomegranate seeds with a cream of Thai coconut and vanilla.
