two phones with the same number; an iphone and a flip phone

My tween daughter has an iphone which she rarely gets to use because I prefer she not have so many distractions. But I do need her to have access to a phone over the summer so am considering letting her use a flip phone. Can we add a flip phone with the same cellphone number, and just put away the iphone 15 for use only on the weekends for facetime calls with the grandparents?