Rocket Propulsion Elements by George P. Sutton, Oscar Biblarz (2000, Hardcover, Subsequent Edition)

Now evolved through many expanded editions, Sutton remains a top-flight all-around general-purpose overview of rocket propulsion. Covers the spectrum from solid and liquid propellant motors through advanced nuclear and ion-drive engines. Plenty of formulae and algebraic equations with detailed explanations of the science and engineering involved in the design, development, production, and testing of rocket engines. Since the text is very comprehensive, covering a wide range of topics, you'll want and need other books to complement this one before you start designing your own rocket, but this is as good a place to start as you can find. Probably a bit advanced for most high school level students, but a valuable reference for any serious science shelf. Too bad it's so pricey.