If those people lectured at all schools in your area, I suppose it hardly had anything very much to do with the fact you went to a Catholic school...
And I guess they went for, shall we say, "simplifications". It may sound ludicrous to you at your age but I imagine that, for example, an idea behing telling young teens they cannot get STDs when they use condoms could very well have been opting for "the lesser evil"; yes, these is still a chance of contracting STDs and getting pregnant but 'if we tell them that the kids may think it is not worth bothering to use condoms at all'. And the possibility of semen transfer form the anal area to the vaginal cahnnel is not all that unlikely, after all.
Believe it or not but I rather suspect that even a well-meant desire to approach various sexual issues in an "age-appropriate" way may sound rather "amusing", or somewhat incorrect, to an adult. But on the other hand, when lecturing on, well, anything, do you not try to take in the consideration the age of those who are going to listen to you? I guess you do.
And oh, if you want to know what a genuinely bizzare sex ed lesson looks like... When we were in our early teens, we got (among other things - there were several lectures of varying qualities) shown a "movie" (and trust me, it is virtually incredible to describe it with mere words, you would have to see it to "appreciate" how insane it was) of sorts that was supposed to explain sex and pregnancy. It was set in quasi-medieval castle (and, by the way, the acting was truly atrocious!), yet it involved 'modern' things like sanitary pads. A prince was marrying a princess; fast forward to the wedding night scene - the narrator (in a voice that was as boring as they get) said "the princess was now a full-grown woman", and the young couple had sex (while the narrator kept on making comments of the "the prince had to be gentle since it was his love's first time" sort). Fast forward a couple of months - there was a shot of the princess throwing up into a bucket while the prince was at a joust; the narrator chastised the prince for not being at his pregnant wife's side - the prince looked shocked and ran home, to lovingly (imagine the most idiotic facial expression in the world) lay his head on the princess' belly... (It also mentioned that because the princess was pregnant, she did not need any sanitary pads or tampons because she would not bleed until she has given birth - and this, too, can easily be incorrect, plenty of women have "quasi-periods" when they are pregnant.)
Incredible. Ever so badly made. Ludicrous. Yet am I angry or disappointed (or even maimed for life) that they decided to showed us a movie like this? Nope. I am perhaps a bit amused (okay, the sarcastic part of myself is actually very much amused) but I do not feel like I have been "cheated" or "lied to" or anything... It was just a rather misguided, yet probably well meant attempt at sexual education...