Hi a warm welcome to the site. If you have the
level 2 CYPW handbook pages 149+ explain how you respond to concerns about a colleague.
Also use your setting's whistle-blowing policy or its safeguarding policy to know exactly what's expected of you in these situations, and so that you know the chain or line of reporting eg. your manager, Head teacher.
One identified way includes speaking directly to your setting's designated safeguarding officer. This is so that what you have to say doesn't become information that everyone can go on to use in anyway they wish. By talking to the most relevant person about your concerns you protect the person whose practices you are questioning.
If your concern is not being addressed or maybe your concern is about the safeguarding officer themselves you follow the line of reporting as stated in the setting's policy eg. your local social services emergency department or OFSTED/local inspectorate if you work in England.
Best wishes