Should guests dress casual or formal?

At most Bar/Bat Mitzvahs, all guests are encouraged to dress semi-formally and conservatively (at least for the ceremony portion). It is an honor to be asked to attend someone’s Bar Mitzvah ceremony and guests should all respect the rules and restrictions of the synagogue. Typically girls wear dresses or skirts that are knee length with covered shoulders (maybe with a sweater or shawl) and a conservative neckline. Boys are encouraged to wear long sleeved shirts with ties and if they are Jewish it is custom that they wear a kippah (skull cap). Girls may also be encouraged to wear a tallit (prayer shawl) which is handed to them when they enter the synagogue.