I doubt these teachers have a morals clause in their contracts. You're asking that the people involved be fired for engaging in immoral behavior, which is a purely subjective standard. Now, in most states, your employer could fire you for engaging in immoral behavior off the job, but since these are government workers, that's tougher to do. They'll probably be covered by a collective bargaining agreement which will probably have an illegal conduct clause, but is unlikely to have a morals clause.
As an employer, you could fire somebody for engaging in what you consider immoral behavior. If I was an employer, however, I would not be interested in my employees' private lives unless they impacted on their job performance.
"Now, in most states, your employer could fire you for engaging in immoral behavior off the job, "
Not unless you have them sign a morals contract first. Of course you could make up some other reason to fire them but if you fire someone for morals they can not only claim unemployment insurance but could also sue you, assuming it was worthwhile.