Hi Y.,
Sending your child off to public school for the first time is indeed stressful. More so for parents than the children though. It's symbolic of them growing up and becoming independent which can be a bit scary. I was feeling it too when it was time for my son to go off to kindergarten. My friends and I decided to have an "off to kindergarten" party before school started. The kids decorated pencil cases and we packed back packs with school supples and presented to them at the end of the party. They had a blast and still talk about it now two years later. Of course, the party was more for us moms than anything else.
I found that schools aren't as helpful with information as I expected as well. Larger elementary schools, I think, have a harder time with this. You have to continue to be proactive. Keep calling them until you get the information you need. You won't be the only mom calling and asking the questions you're asking. I'm sure you'll have plenty of company.
As for the clothes, I don't know what you think about ordering online, but it makes it so easy for me. I just ordered a whole wardrobe for my 7 year old in about 20 minutes...couldn't have been easier. Use a retailer you're used to though so you are familiar with their sizing.
Extended day covers the early release days with exception of a day or two (ie., last day of school). I've calculated approx. 45 "0ff" days per year for my son. That's a lot. If you and your ex or your mom can help you, that would be ideal. Otherwise, you'll have to pay to put your daughter in daycare (about $20 per day) on those days. Be sure to factor in the 2-3 weeks before and at the end of summer camps. It's not easy handling kids school schedule, but you learn how to manage with the help of your support system. Good luck!