I would keep the first sentence, then add the one about your brother. Then say you like U2, to sleep, and to ski, and then add the rest (calm, smart, and funny)
Also, i would add “and” (et) the same way you would in english. So, for example, “i’m 15 AND i was born at St. Paul on June 9th.” also, I have a brother, he is 10 AND his name is Matt”

EX: (i’m not sure if this is write, but i think it flows better. My teacher likes our ideas to be grouped)

Bonjour! Je m’appelle Antoinette. J’ai 15 and et je suis nee a St. Paul le 9 juin. J’ai un frere, il est dix et Il s’appelle Matt. J’aime le musique, et le group de U2. J’aime l’ecole et du (le?) ski. J’adore dormir! Je suis calme, intelligente, and amusante.

Now, i think this sounds better but its up to you as this seems like an assessment for your teacher to see what’s up with you and french. And don’t trust my spelling… i just re started my french classes this week so i’m a little rusty!

Good Luck!

There is an accent aigu on the e of née and école.
An accent grave on the e of frère.

l’m wondering who gave -1 to mememe. Her text is quite right. Just exept “née”.

Bonjour! Je m’appelle Antoinette, j’ai 15 ans, je suis nee à St. Paul le 9 juin. Je suis calme, j’aime dormir. J’ai un frère, il a dix ans, Il s’appelle Matt. J’aime la musique, et le groupe u2, je suis intelligente, j’aime l’école. Je suis amusante, et j’aime le ski.