Why not ? I would argue that most teachers provide a more valuable service than most lawyers (For my definition of value atleast). Lawyers have strict licensing requirements while teachers don't, which would be one of the major differences
Teachers have strict licensing requirements in literally every state.
Although the bar exam specifically is probably harder than any single component of teacher licensure, overall they are comparable, as teachers have more components.
In NY, teachers have to pass exams, and get certified. I could ask my friends for details, but I know they need to do it, because I hear them bitch about it.