What is the burden of demonstrating the invalidity of classification in this case?

9] The burden of demonstrating the invalidity of the classification in this case rests squarely on the plaintiff as the party assailing it. (Schwalbe v. Jones, 16 Cal.3d 514, 518, 128 Cal.Rptr. 321, 546 P.2d 1033.) The case is not one in which fundamental rights are involved. Nor is it one in which the classification is suspect. (See Brown v. Merlo, 8 Cal.3d 855, 862, fn. 2, 106 Cal.Rptr. 388, 506 P.2d 212.)