Guys in my history cl (i'm in college, history is an extra course) make 'pencil' jokes?

they are soo immature. they make up a bunch of pencil jokes like saying slowly, "cause i think you wanna put the PENCIL in the SHARPENER" and then the other guy is like "dude you're nasty" but he laughs. and oh buy 'pencil' he means and by 'sharpener' he means . well, actually they're jokes. if somebody is like sharpening their pencil or something jamming it in the sharpener to do sumthing or other they're start laughing and they're like "oh my god!" they seriously need to grow up they're like 18/19 years old, not 11!!!! so annoying... what is your opinion on this?