Not so, no state may pass legislation that voids or goes against a portion of the US Constitution - sounds like the equal protection clause.
Historically the states were indeed free to establish religions -- unless their own constitutions prohibited this, as most (I don't know how many) now do. Massachusetts was the last state to have such an institution. Their church (Congregationalist, I think) was disestablished in the 1840s. After the so-called Civil War, the US Constitution has been re-interpreted to "incorporate" most of the Bill of Rights into the 14th Amendment (no state can deny anyone life, liberty, and property without due process), so now it's not possible for a state to establish a religion, regardless of the state's constitution.
That has no bearing on your original post which read,"If a legislature passes a law banning the teaching of evolution OR requiring the teaching of a religious precept like creation of ID, it is violating the First Amendment by both requiring the teaching of one sect's religious views and by favoring one Christian sect over others." Your original post is false. State legislatures would not violate the 1st Amendment if they passed either of those because the 1st Amendment prohibits only the federal congress.