Isn't the school under some sort of obligation to keep the parents informed? ...
A pregnancy isn't anybodies business but kids oding (or even caught with substantial amounts of illicit drugs) on school property I would expect an email with details. I mean, that sort of thing is open record from the police reports.
I'm actually not sure that the schools are required or motivated to inform parents of issues of this sort that might reflect badly on the school. Our local area has had a couple of high profile instances of teachers or other school employees caught having sex with high school students in the past few years. The last incident prompted a state wide (I think it was state wide) change in policy requiring schools to notify parents when there was an allegation of sexual abuse by a school district employee. After that policy change, it came to light that there had been a few other instances in the past few years locally of 1) a teacher and a student caught naked together, 2) a school district employee accused of sexual assault on a student and he had a prior record from another state of this sort that hadn't been caught when he was hired.
The schools, when asked why they hadn't notified parents of these events, told the local paper that they thought it best for the students who were involved for there to be no media attention. Someone else in the paper hypothesized that the schools thought it best for themselves that there be no media coverage.