Subject of "has been internalized" ?

Hi~ What does the phrase "that has been internalized" modify in this context?

The same bias? OR change ?

It's so confusing to me and I would like to hear your opinion.

Any comment would be welcomed.... Thank you in advance~

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bias is developed by two things consistently
being linked together in the environment. Once the linkage is established,
the brain will make the association whenever one of the elements
is recognized. For example, if black students represent only 10 percent of
the student population and 50 percent of suspensions, then teachers will
eventually connect black students to misbehaviors resulting in suspension.
These types of biases develop over time regardless of personal values.
Teachers determine daily the pace of learning based on when the
majority of students understand the material. It is only logical that this
same bias impacts behavioral interventions. The teacher applies the
same bias of how long change should take that has been internalized by
constant observation of students over the years. This bias occurs even if
the teacher is aware that all students are not the same. This is where
teachers have to fight the urge to continuously attempt new behavioral
interventions if the current one is not quickly successful.