Can a state "opt out" of Hazelwood v. Kuhlmeier thus preventing school administrators from exercising prior review over a school publication?

The thing that is very important to realize here is that
this case does not tell states or school districts what they
must do.  Instead, it tells them what they
may do.  In this case, the Supreme Court told the Hazelwood
school district (and others) that they were allowed to have their principal censor a
part of the student newspaper that was, in his opinion, contrary to the educational
goals of the school district.

However, this is not a
requirement.  The Supreme Court did not tell all school districts that they had to have
their principals censor school papers.  This was a case that was about saying when
schools could abridge their students' First Amendment rights, not one that was mandating
when schools have to censor their newspapers.

So the answer
to your question is that states do not have to "opt out."  There is no requirement
imposed by Hazelwood.  This case merely tells what schools
may do and it is up to the school district or state to
decide if it will take advantage of this ability.