This story (the one that isn’t mine) comes from D.
Bas mitzvahs are an issue for bais Yaakovs. Something not all aidel bais Yaakov maidels know: bas mitzvah celebrations are a creation of the Conservative Jewish movement. Conservative young women get to lein at their bat mitzvahs*, which obviously isn’t going to happen in an Orthodox setting. But somehow, the celebration of reaching the age of maturity and responsibility has leaked through, and bais Yaakov has ceased to fight this modern (and possibly feminist?!) concept.
They still have to deal with the question of: how much of a celebration is acceptable? Should a girl be allowed a hall and caterer and extensive guest list like her brothers? Or, is something smaller and more modest befitting the role of a bas Yisroel?
Most bais Yaakovs take the latter route, and exert varying levels of control over their 6th-graders’ birthday parties. In my school, the rule was that all bas mitzvah parties had to occur in the school lunch room, there had to be a dvar Torah, and the entire class had to be invited.
There was a little bit of grumbling, mostly about the first rule. The lunchroom was awkwardly shaped and ugly, the kitchen wasn’t allowed to be used, and by dint of being our school lunchroom, it was a bit of a damper on festivities. (Possibly, that was the point.) But ultimately, most people brought their relatives to school, served lukewarm lasagna over sterno, and were satisfied.
Other schools had different rules, often born out of different stimuli. After one party included a guest belly dancer and, allegedly, mixed dancing (???), one school simply forbade inviting anyone from school to a bas mitzvah celebration. (I guess that was easier than trying to control the celebration itself.)
One student of that establishment, D, recalls her friend emerging from the principal’s office in tears, after the administration found out that she had invited her school friends to her birthday party. D had been one of the invitees; she went to the party; for this sin she had to write an apology letter to the principal and administrators.
One student, anticipating being the center of attention at a big event, had gone and bought herself a bas mitzvah gown. (This was before they announced the rules.) She was very disappointed to find its use relegated to a small affair mostly populated by aunts.
To assuage the natural disappointment of the students, the school decided to replace the individual coming-of-age celebrations with a trip to Kids n’ Action (an indoor play space) and a bas mitzvah gala celebration.
The gala included a play about the founding of bais Yaakov (with the usual excursions for tznius). The girl with the dress got to wear it after all — for her part as Sarah Schnierer. Other students approached her asking the famous seamstress to shorten their skirts to match the latest fashion. In her (fashionable but tznius) dress, she informed them about the importance of interior, the transience of materialism, and the scam that is fashion.
What rules did your school have around bas mitzvah celebrations? (And for the guys: bar mitzvah rules?)
*For further info on the women leining situation, I have this page with sources.