What change occurred regarding teachers' professional conduct when the Nazis took control?

The requirement for teachers to take loyalty oaths when the Nazis took control was significant in establishing a regime of strict ideological conformity within the education system. The Nazi government sought to ensure that educators were fully aligned with its policies and ideology, which included promoting anti-Semitic views, militarism, and nationalism. By enforcing loyalty oaths, the regime could root out dissent or opposition among teachers, who play a crucial role in shaping the minds of future generations. This measure was a part of the broader Nazi approach to control various societal institutions, making sure that they contributed to the state's objectives and indoctrination efforts.

In contrast, the other options do not accurately reflect the key changes regarding teachers' conduct under Nazi control. There was no new requirement for teachers to specialize in subjects that was unique or mandated by the Nazis. While performance evaluation existed, it was often overshadowed by the emphasis on ideological adherence rather than actual student success. Lastly, the formation of unions for teachers was not encouraged; instead, the Nazis aimed to eliminate independent unions and replace them with state-controlled organizations that furthered their political agenda.