I found this Australian article:
www.bodyandsoul.com.au/sex-relationships/relationships/domestic-violence-10-warning-signs-of-an-abusive-relationship/news-story/731d1d079e87573c329e0dc8fd5863ba?utm_source=SEM&utm_medium=cpc&gclid=EAIaIQobChMIjNjejYr_8wIVFIBQBh2P5wUkEAMYASAAEgKNHfD_BwE
This part is exactly what your DS is enduring:
Signs of an abusive relationship:
Control is a cornerstone of an abusive relationship.
One sign of control is that the abuser will try and isolate the victim from his/her support system and over time limit contact with family and friends who can provide support. This may even include moving away to a different area.
Showing a partner disrespect – telling lies about the victim to friends and family, belittling, name-calling, withholding information.
Making threats and forcing the victim to comply through fear.
Extreme possessiveness.
A constant assertion of control is a cause for concern.
This may include controlling information that the victim would otherwise be entitled to receive, monitoring their every move as well as text messages and calls, asking for explanations of whereabouts or preventing a partner from getting a job.
Gaslighting – this happens when the abuser distorts the reality and makes the victim doubt their own perception and sanity. This is most often done with the intention of confusing the victim.
Denying the freedom and autonomy of the victim, limiting access to money, imposing extreme budgeting measures, hiding financial resources and information.
Trying to turn the children against the victim and telling them that the victim is a bad parent. (In your specific situation it’s turning your DS against you)
Disregarding boundaries is a cause for concern. Maintaining healthy boundaries is the sign of a healthy relationship and provides a person with the opportunity to maintain his/her individuality. If the behaviour is not within your comfort zone make it known.
Making demands regarding the sexual relationship and forcing a partner to have sex.
Physical aggression may also be threatening looks, aggressive gestures, or destroying property.
Unpredictable mood swings – if one partner has an unreasonable reaction to an otherwise simple disagreement, it is a cause for concern.
Also, if a partner gets withdrawn or extremely angry without reasonable reason.
Ignoring the situation won’t make it go away.
Usually, victims of domestic abuse are unable to leave as they don’t have access to money and they are ashamed as they think they will be judged.
When a victim decides to leave, the perpetrator knows they are losing control and this can be a very dangerous time as they try to repair the relationship and regain control. So have a plan in place that will carry you through. Once a decision is made to leave ensure you get the support of those who can assist you with the plan you have made to leave.
Anne-Marie Cade is a nationally accredited mediator and conflict resolution specialist.
I would look at this list as a template and plot the evidence against it with specific incidents that have happened to your DS. The school need to see this. If they ignore this evidence take it to DSS:
www.dss.gov.au/our-responsibilities/women/programs-services/reducing-violence/help-and-support