hello.... i am new to this so plz be patient if I get it wrong. Firstly I should tell u i am a yr 1 teacher and thus deal with chn a little older than yours all day. I am also a mum of two teenagers , most of their lives i've been a single mum . I sympathise with the getting dressed thing , i used a have a similar problem with my son ( who is now almost 18) and I solved it by refusing to fight with him about it , it was getting dressed for school that was the issue . What i did was stop fighting/nagging and took him to school in his pj's . Of course, by the time we got there he was dressed in his school clothes in the car. Fastest dressing you ever saw. Sometimes kids do this stuff because you react ... mine still try it.
hope this helps
annie