Whew--not sure where your health teacher got his/her information, but according to the latest research, condoms, when used in normal life (ie. including people using them incorrectly), are 82% effective. When used perfectly they're 98% effective! bedsider.org/methods/male_condom#details_tab
In the survey that inspired this campaign, unmarried young adults were asked whether pregnancy is "much less likely to occur if a couple has sex standing up." 18% of the guys said it was. The fact is that pregnancy can occur if a couple is standing up, sitting down, lying sideways, or in any other position you can think of and that sexual positions are no replacement for birth control.
Oh, and to clarify, when I say "much of an effect," I mean, ANY effect at all. @ressings8 @Kanashto @webmastertool @ConanCnutKicker @nickmsss2