I was NUTS about this series in elementary school. The conceit is that it's a group of kid detectives - there are four of them, with the initials T, A, C, & K. They choose T*A*C*K as their acronym/code name because weaving back & forth, or tacking (heading to starboard, then to port) is how you head in a straight line in sailing. Probably the introduction to my lifelong love of cozy mysteries, definitely my introduction to the illustration work of Alan Tiegreen, and a staple of my mid-80s monthly Troll/Scholastic book club order.
A random book in a box of hand-me-down books from a neighbor who moved away when I was a kid. I read it totally loved it. Loved the idea of a group of kids solving mysteries! This was probably the start of my interest in the mystery/thriller genre.