The class in which I dissected a frog, was in high school.
I've never seen a science course which allowed students to "play with the parts", nor have I heard of it. Is it common for students to make jokes? Sure. Is that acceptable? To a degree. To what degree? A very limited one. Some use humor or nervous laughter to adjust to situations which make them feel uncomfortable...to that degree it's understood and often allowed. Beyond that, no.
Which is true of any class, otherwise the teacher simply isn't in control of the students, which clearly indicates a serious problem with him or her.
Additionally I've never seen dissection of any vertebrate done prior to 8th grade, any dissection earlier than that is usually done with gifted students in advanced science courses (or by instructors who feel they can cover the material, usually in private schools) and involves worms.
Perhaps you can point out any done earlier than that. Otherwise it's earth science in 9th grade (physical science which is the precusor to physics and chemistry for advanced students), biology in 10th, chemistry (elective) in 11th (lab for advanced students) and physics in 12th (advanced only). And the only dissection that takes place in any of those courses, is in biology in 10th grade.
And it is always optional. Meaning that students can take the 'F', or as is more common (but does not always occur) they can do an alternative assignment. Most instructors who do not allow an alternative assignment by choice, do allow it if/when a student cannot handle dissection...which does happen. And it's done that way because there are MANY students who don't believe they want to or can do it...who once they do it find it fascinating and get quite a bit out of the assignment.
Your assessment of students, based I can only assume on your experience, is really...really fucked. Either you had an incredibly shitty teacher or you were in a very lousy district. That can happen too...but it doesn't make it the sum of all experiences.
I'm not just basing it on my experience either, especially since Catholic school education is very different in most respects from public school (especially since they could and did HIT students when I was a child
and yes I was hit). But I'm also basing it on my own observations in classrooms (because I've been considering teaching in science) as well as the experiences of my friends children who are now mostly in high school or college (jesusfuck I feel old) and many friends who are educators.
Including my mom.
Who quite frankly my biased opinion aside, is probably one of the best teachers I've ever met. She tolerates no shit in her classes and was always the one teacher kids seemed to be afraid of (in the 'ooo you're in troooouble' way) yet still has students 20 years later who remember her and stop by constantly. She's commonly listed as their favorite teacher of all time. Which is just an aside, but one that makes me personally proud of her. (And if I do teach, I seriously doubt I'll ever be as good quite honestly.)
I've also seen bad teachers who failed to control their classrooms too. 99% of the time truthfully, it was their own fault. I've seen it in 'good districts' and I've seen it in bad ones. It doesn't make them bad people or anything, it's easy to lose control, and once lost...almost impossible to regain. But that was also a lesson I learned young seeing a long term sub come in, and lose complete control of a class (to the point where students were abusive to her) and when she later taught at my high school she had no such problem. Whatever mistakes she made, she didn't make them again. And she lived locally to me (nice older lady in her late 60s) who later thanked me for never telling other students about her out of control class. (I didn't mention that my own mother pulled me aside and told me I was never ever to mention it, and why...
).
Anyhoo...the belief that students get no value from it, is easily disproven by the many students (myself included) who DID get educational value from it.
As I said previously you CAN have completely valid opinions which are pure opinion...such as the belief that the life of an animal is worth more than such an experience, etc. I won't agree...but it's a valid opinion for someone to have.
But that *some* students abuse educational tools, or refuse to avail themselves of it...we might as well argue against computers in school because some computer instructors are fat lazy slobs who let the kids play video games all day and surf for porn. Because it may occur doesn't make it commonplace, or standard.