Sims 3 Children Keep Skipping School

When the children get onto the bus they won't go into the school building and instead work on already completed homework. Even while they are on the bus, it'll let me choose how they do school (Work Hard, Meet New Friends) but still they end up outside and doing completed homework. To add to this it says 'Skipping School!' and the earliest it will allow the children to attend school is 9:58. It also messes with their grades because their homework is 'incomplete' and they're late. The expansion packs I currently have are Late Night, Generations, University, Seasons, Pets and World Adventures. I have had all of these expansions for a while now and have never had this problem before. Anything will help, thanks.