The Super Spies are students.
They are not really spies. Except they do a lot of spying so in a way they are. They do not work for any organization, though, and the name 'The Super Spies' is one they came up with for themselves so it sort of counts but not really.
The group in question consists of three girls:
Sarah Cole - a ninth grader with shoulder-length honey-colored hair and green eyes.
Jackie Jenkins - a tall, skinny ninth grader with a "mop of wild curls".
Lacey Cole - younger sister of Sarah, an eighth grader (I think), with similar blonde hair as her sister but extending to her waist.
The action for the adventures of these three young ladies take place in the small town of Harrisburg in Michigan. The two Cole girls are temporarily staying with their aunt and uncle for the summer while their parents took a vacation trip - this would get more serious when it is learned that the parents mysteriously and frighteningly disappear! That will turn out to be another case/mission for the Super Spies.
It is just a day or so after arriving in Harrisburg that Sarah will meet Jackie, who introduces her to the myth about the town cat lady being a witch and when the two follow that somewhat scary woman, they will lay the groundwork for becoming suspects in that woman's subsequent murder and that perceived need to prove their innocence will lead to a desire to catch the actual killer(s) and that is how they came to form the Super Spies.
Once they got a taste of the thrills of investigating (and, to be honest, snooping) and finding they were actually pretty good at solving cases, the desire to find more cases to take on will prove irresistible.