Online safety is part of safeguarding and it is recommended that there be some inclusion of online safety within the safeguarding policy.
With regards to the online safety policy; it is suggested that a structured, modular approach be adopted. Having an overarching online safety policy (which is short and easy to review) with separate but linked individual short sub-policies/Information Advice and Guidance (IAG). It will be these latter ones that are likely to need frequent updating.
Once in place it is important that your policies and IAG are well managed and that all stakeholders are familiar with them to apply them appropriately, this may include specific training or just advisory sessions.
It may be useful to include student representation in the review process thereby helping the whole school to own and understand why policies and guidance are in place. Acceptable Use Policies (AUPs) may need revising and signing by the parties involved, this may include any home/school agreements that refer to the use of technology.