Hi, if your children & parents use any of the main school's property/building/land you can use their policies & procedures alongside any different policies & procedures that your setting might of developed.
page 119 of the level 3 handbook looks at how parents leave their children in a setting with the expectation that they'll be safe and free from harm. This is also every individual's human right -
article 19
Pages 120+ go on to show how the collective policies and procedures that your organisation has, guides the way you do things. This ensures that all practice is lawful and meets legislation, regulation, workforce standards.
Best wishes