Not bad considering it's an interclass competition. Usually high school kids are just lazy, especially to sing in a soprano-alto-bass harmony in a big group xD so good job!

things to work on : pronunciation, especially if you're going to sing in a language which you're not used to speaking. Making is sound less cina would impress the judges a whole lot, adds proffesionalism!

as for the head sway thing, they usually do that in choral speaking in my experience and ask them to smile moooooooreeeeeee x) search you tube for song suggestions.

good luck!