If they do this in a biology class, this would not be academic freedom. It may be freedom of speech, but could also be seen as disrupting teaching activities - and so subject to disciplinary action.
If students use derogatory slurs against each other at that time, universities may decide this not only disrupts teaching but is threatening, humiliating or intimidating and so may take disciplinary action.
What about outside classes?
Universities will need to ask similar questions if derogatory slurs, personal attacks or loud aggressive arguments or chanting occur in university corridors or elsewhere on campus.
Although the students or staff would still be exercising their rights to freedom of speech on campus, the manner of this speech can be regulated. Is aggressive chanting disrupting teaching or research? Is it threatening, humiliating or intimidating students on campus?
Under the model code, universities can ban visiting speakers if a speech is likely to be "unlawful", "prejudice the fulfilment by the university of its duty to foster the wellbeing of staff and students" or,