Knock knock can any HT's help?

[insanityscratching]

Dd's school failed to follow their own safeguarding policies. It's pretty straightforward, there is no disputing it as it's all documented. Fundamentally I alerted school (SENCo) to dd's self harm twice and neither time was it passed on to the person responsible for safeguarding. That she denied I had and then retracted when I sent copies is another matter. There is also the issue that twice dd was sent out of school bleeding through self harm, nothing was documented and no support was given even though dd has full time TA support through her statement.
The person responsible for safeguarding is investigating and wants me to give her a chance to address the issues ie inadequate support and poor communication first so as to avoid a formal complaint.
What I want to know is, is a formal complaint the only way to ensure that the school learn from this? I don't want blood even if this is the latest in a long line of issues although I do expect a decent apology from the SENCo as well as the support and communication issues addressing.