Valentine Day is a student at a spy school.
You would figure from the name for her adventures being "Vi Spy" that she was already a spy - the Vi in this case being her nickname which is a whole lot easier to say than Valentine and doesn't automatically make you think of hearts and smaltzy (Okay, I admit it, I like 'em!) cards and chocolates. But, nope! Not really, yet, although, well, kinda yes, too.
Our Vi Day, aka Vi Spy, is twelve years old so is not even quite a teenager (but soon, if she lives long ...).
Her mum is Easter Day, a former super-spy with [I believe, the British] Secret Service. Her soon-to-be-dad is George Sprout, who is one of Vi's teachers and is really lovely but really quite dull (according to the author). Just for the record, her grandmother on her Mum's side is named Independence Day, great-grandmother was Christmas, and great-great was Mother Sunday
Now at first I thought with a nana named Independence Day she might be an American citizen but since we learn early on that her family is a mixture of "Senegalese, English, Jamaican, and African American heritages", well, who knows which Independence we are talking about. I will stick with the American nationality but I won't argue about it.
Mum used to be a spy and so did her late Dad, Robert, who died "diverting a nuclear missile into space one second before it exploded in the Earth's atmosphere". That is when Mum decided to retire to raise Vi because she needed a stable parent, one "who wasn't going to die in a tank of mutant piranhas".
Learning about her parents's history is what opens Vi to being able to attend Rimmington Hall Espionage Academy because "all the greats go to Rimmington Hall". It seems that Vi "comes from a long line of great spies, going right back to the days of the underground railroad in 19th Century America". And that is how she became a student spy on her way to being a real spy.
And the wedding I mentioned above gets kinda messy when dear-but-dead Dad shows up and it turns out he was not a super-spy like Mum saving the world but was really a super-villain and ... well, things get big-time odd after that.
Oh, something else that is kinda cool about Vi Day is that she loves to be a 'putpocket'. That is sort of like a pickpocket except you take something from somebody's one pocket and put it in another; it confuses them no end and is pretty funny to watch.