Short story, year 8 kids pissing about and girl throws blazer on floor. Boy picks up blazer and walks off. Ds says; why are you carrying her blazer around school and throws it back on floor. Subsequently phone is now smashed. Girls mother is messaging me demanding I buy her a new phone. Haven't replied yet. Very reluctant as my ds had no way of knowing phone was in blazer or it could have broken when girl initially chucked blazer. Advice please