It is important to remember that issues in regard to radicalisation and extremism are safeguarding issues, and the same level of risk assessment and proportionate response are required.
You can read the departmental advice for schools on the Prevent Duty
Alternatively you can also refer to Keeping Children Safe in Education for further information or our Safeguarding and Child Protection policy.
The school safeguarding policy outlines the considerations and referral procedure that schools and settings should make, in that wherever possible (immediate risk of harm notwithstanding), concerns should be shared with the Designated Safeguarding Lead in school and dialogue should take place with parents/carers. However, where there is imminent risk of harm to a child, an immediate referral should be made to Prevent, as with all other safeguarding concerns where risk of harm is imminent. If there is concern about risk of harm to others, then the Police should be contacted as a matter of urgency.
Discussing such issues as a family is not easy. Some useful advice can be found here