My father was awarded a higher pay grade (Grade 86) by the court, but the management committee still hasn’t given him the salary increase. Is this legal? Can they simply ignore the court’s decision?

No, it is not legal for the management committee to ignore the court’s decision. The court order is binding on all parties involved, including the management committee. They are obligated to comply with the court’s decision and provide your father with the salary increase corresponding to the awarded pay grade.