Old text books can be a nightmare. I taught my kids from their "first, second, third, etc... grade reader" series which were from my grandmother. They were published in 1908. The problem was that the third grade reader contained vocabulary and sentence structure used in college courses. In other words it took a hundred years to dumb a college course down to the third grade level.
As to the number of dairy groups served a day, or the treatments for AIDS, just what the hell does that have to do with education?
If you use text books from the late 1800's and early 1900's, you'll get a college education by the eighth grade.
Old text books can be a nightmare. I taught my kids from their "first, second, third, etc... grade reader" series which were from my grandmother. They were published in 1908. The problem was that the third grade reader contained vocabulary and sentence structure used in college courses. In other words it took a hundred years to dumb a college course down to the third grade level. But, dumbing down school and college serves one great purpose - to provide job security for the teachers' union membership and for the Vietman protesters/college professors. Very self-serving circle of educrats, but little benefit to those that they are entrusted to teach.