Let me begin by stating that, despite the suggestions of the poorly animated talking blunt in the beginning of the movie (no, seriously), I was not high when I watched Mac and Devin Go to High School. Unfortunately, you would have to be stoned out of your mind to find anything in this movie even remotely funny, and so I sat through the most grueling and painful movie experience I've ever had the extreme displeasure to be subjected to.
In plain terms, there is a very real possibility that this is the single worst movie ever made.
But hey- I haven't seen every movie ever. There is a (small) chance someone managed to make something worse. I just doubt it. Every aspect is just so... stupid. The jokes would be funnier if you tried to make stupid jokes. The music is a sad attempt at a washed-up, has-been rapper to remain relevant.
But by far the worst thing is the plot. Presumably, Snoop and Wiz payed a small fortune to a group of preteen boys who just discovered weed, curse words, and girls (in the same ten-minute span) to write the first draft, forced at gunpoint a single homeless man strung out on crack to edit it, and then gave it back to the preteens for the final script.
Yes, this movie was low budget. But why? Could Snoop Dog, easily one of the most successful rappers of all time, not get a real producer? Hire someone with a tiny sliver of talent to do the effects? Hire an actor who could actually act? No. Because no self-respecting person would have anything to do with this movie. In an industry that would buy almost any script, no one would invest a nickel in this movie. It would be so much easier to just tie their career to a post and shoot it.
If you like extremely stupid pot jokes, incredible headaches, vast stretches of mind-numbing boredom, and watching a 40-year-old man pretending to be a high school-er, knock yourself out. Also, please get out of the gene pool before you manage to make humanity even worse.
But if you have even a tiny shred of self respect and/or an IQ over 7, please, just walk away. If you really, really just want to watch a terrible movie, go watch The Room. At least The Room is so awful it's funny.