I wondered the same thing also when I took high school chemistry and, again, in college when I took introductory physics course.
The reason why these books state this is because the Schrodinger Equation is a partial differential equation.Thus it takes several semesters of calculus, multivariable calculus, linear algebra, differential equations, and partial differential equations. Then as you take quantum mechanics and learn about the Schrodinger equation you're exposed to even more mathematics (spherical coordinates, group theory, Hermite polynomials, and so forth).
In addition, a number of physics courses are very helpful in understanding the derivation of the Schrodinger equation itself(especially classical mechanics).
In other words, if you saw the equation it wouldn't make that much sense understanding it mathematically. Also the equation takes on many different forms according to the system it is defining.
However, there are books that discuss the nature and give you a great flavor of what the Schrodinger Equation encapsulates (Quantum: A Guide For The Perplexed Jim Al-Khalili).