I have not researched the issue (and I will) but at a first glance it seems that it maybe more related to the state of economic affairs in EU, rather than Bulgaria itself. I am not sure whether you are aware of this, but as a EU member state Bulgaria had to bring its legislation in compliance with the EU legislation (and that also includes the area of education). In addition, there may be different requirements for the teachers and their qualifications depending on whether the school is a public or private institution. All this being said, I am not excluding the opportunity that whoever was responsible for writing the act itself, did not do a very good job, and therefore, revisions maybe needed.