Teachers are "authority figures" because their knowledge of education is recognized, accepted, and legally certified. Children ages 5-9 are not always capable of self-governance and sometimes need the guidance of an authority figure to resolve conflicts.
The "change they wanted" was for social harmony among students, and it was accomplished using rules that the children created and agreed upon.
The Legotown “leaders”/“builders” that the teachers disempowered were authority figures because their knowledge of Legos was recognized and accepted by the other children. There wasn’t much conflict (just submissive acceptance of the builder’s governance by the non-builders, and animated discussions on what to build together between the builders) until the teachers intentionally synthesized some with their Lego “game” in order to engrain their own preconceived biases (“critical judgments about people who have wealth and financial ease”) into the kids.
Very similar how communist revolutions happen. Inequalities are identified the people rise up and everything gets burned to the ground. All the old leaders removed and need inequalities spring from the ages.
Please note that the situation was resolved by the teachers utilising their position of power to impose the change they wanted. They want democracy and egalitarianism but it turns out they needed authority to impose that.
Highly ironic.