Life is not separated into subjects, we do not get told, "Now you will be using your english skills and now your science ones". It makes sense to me that school education should be reflective of the world that our students will be living in. Primary school does this really well and I think high school could recreate some of the things they do. Don't get me wrong I do think there is value in specialisation, in getting involved in a subject to develop advanced technical skills, however not everything should be like this.
These three steps are how my school has integrated specific subject areas at a Year 9 level.