March of the Vanderpants

Pick a book. Grow a Reader!
This series is part of Scholastic's early chapter book line Branches, aimed at newly independent readers. With easy-to-read text, high-interest content, fast-paced plots, and illustrations on every page, these books will boost reading confidence and stamina. Branches books help readers grow!
In book 12, the S.S.M.P. needs to track down the boss-monster and get their monster notebook back! Alexander, Rip, and Nikki are keeping their eyes open for clues. Then Alexander spots Principal Vanderpants carrying a white bucket filled with spaghetti through that mysterious locked door on the 13th floor. Why is the principal acting so strangely? Could SHE be the boss-monster?