There is a lot going on with 5 kids, so maybe some new routines/habits all around can help. (Speaking as a mom of 9 kids, currently ages 15-1, there is just always a lot going on…lol). At my house a couple things help:
1. Give the kids (esp. your oldest you want to dawdle less) a list of what she’s do get done for school that day. Do the together things first so that she’s just left with individual work. And then let her do it. She decides when to buckle down and work. BUT she also learns the consequence for dawdling – she’s stuck doing work in the afternoon or into the evening while everyone else is done.
2. To help her – give her a quieter space to do her individual work. My high schooler likes to take her individual work to her bedroom. My distractible 11 yo does best sitting where there is NO window to look out, and often with headphones on to cut the noise distracting them. One boy likes doing all his work on the floor of his bedroom.
3. Let her know that it’s your job to handle the other kids questions and that she can focus on her work. Teach her to remind the kids “Ask mom.” or “Mom helps you with that.” or “I’m doing my school work, ask mom.”