My son Andrew was diagnosed in August of 2005 at age 12. He was also in the 7th grade. He is now 15 and in the 10th grade. The transition to High School wasn't too bad. Don't get me wrong, he was still nervous. I have an excellent nurse who is very organized. My advise to you is to find out who the nurse is at the school and plan to meet with her before the school year begins and find out how she does things and to introduce your daughter to her. Find out if there are other diabetics in the school. We also have a meeting with the teachers to discuss what diabetes means and to introduce Andrew to them. We also answer any questions that they may have. Some teachers believe it or not have never dealt with a diabetic before. We then set up emergency kits for each classroom consisting of a bottle of water, a juice box, crackers, glucose tablets. The teachers are instructed to carry them with them at class trips or even fire drills or emergency evacuations.
The meeting with the nurse made the transition much easier because he knew what to expect from her and her routines. Most likely she will do her injections in her office. My son was on the pump before he started High School.
You should tell your daughter the importance of letting people know that she is a diabetic. Find out if any of her friends are in her classes. That way if anything happens she has them to speak for her. She should also have a ID bracelet just in case. We also established a signal with the teachers to show if Andrew is in trouble. He raises his pointer finger to the teacher and that shows them that he needs the nurse and his emergency kit. He has never used it yet.
The most important thing you can have for her is the 504 plan. It was the best thing I ever did when he went into High School. He didn't have one in Middle School. You are dealing with more in High School, tests,sports,after school activities,etc.
Just let her know that it's normal to feel this way. I'm sure that everything will go alright.