BM is irresponsible

My boyfriend’s son is 5 and currently in kindergarten. His bm is a disaster and frequently keeps him home from school for ridiculous and often made up reasons. She tells my boyfriend “it’s her time and none of his business.” Is there anything he can do to force her to bring his child to school? I mean, it’s his first week back after holidays and she can’t even get him there 3 days in a row! She is irresponsible and now teaching her son the same bad behaviors that she has.