Great advise already given, just wanted to add my experience.

DD1 is very very tall and was quite adept at climbing/monkey bars on the start of school last year. She seemed to (and still does) drift towards the kids most like her. At the start of school none of the transition kids (your prep) even came close to her shoulder lol. She has her class mates whom she adores, but it did take a few months for her to find her 'place'.