jmc

Let $y=f(x),$ so $y$ can take on any value from $-3$ to 5, inclusive. Then $y^2$ can take on any value from 0 to 25, inclusive. (If we take any value from $-3$ to 0 and square it, we get a value from 0 to 9. And if we take any value from 0 to 5 and square it, we get a value from 0 to 25.) Therefore, the range of $g(x)$ is $\boxed{[0,25]}.$