If You Want To Play It, Then You Have To Say It!
When I first began teaching guitar for a living the hot thing that all my kids wanted to play was grunge rock, specifically Nirvana and Pearl Jam, in that order. The strumming style on a lot of those Nirvana songs was highly syncopated and contained a fair amount of percussive rhythmic strokes, with the guitar strings muted, exactly the type of rhythm guitar playing that leaves the beginning student feeling confused and left me as a beginning guitar teacher scrambling for ways to keep these kids engaged.

First I thought I will teach everyone to read rhythmic figures, strumming patterns, and transcribe the tunes, or simplified versions of them, for them to use as their rhythm reading practice. This approach can work but it is time-consuming and long sight reading lessons are usually not very engaging to kids who are trying to learn to play rock ‘n roll.
Being that I have always felt that perhaps the most useful and practical course in any music school curriculum is sight singing and ear training. I see such a great value in these traditional musical educational procedures and practices that I have tried to bottle that experience for my weekly guitar students with a two pronged attack. First, by asking them to sing the rhythm first, and only then should you try to replicate the song on your guitar. To my amazement, this simple ear training procedure greatly increased the chances of succeeding in virtually all of my students. It works so well I often remind them of this method of practicing by saying if you want to play it you have to say.
I also like to tell them that the first thing I remember about attending the mythical and glorious Berklee College of music in Boston was that I was immediately shuttled into ear training one and a sight reading lab. Although, I found it challenging to the point of being nearly impossible I managed to survive and then thrive under the patient tutelage of some great teachers and my mentor William G Leavitt. All these years later, I have realized that the two torturous courses I dreaded going to have served me incredibly well over my long career as a professional musician.
The second prong of my attack plan is the reason I have lots of very nice transcriptions, done in music publishing software, for easy strumming exercises, guitar standards, old classics and current hits.

Smells Like Teen Spirit Simplified Rhythm Part

I keep them on the hard drive of my laptop and print them as needed. This is my plan for bottling a sight reading and ear training component into private lessons, by being able to constantly prosecute the case for sounding out and playing rhythmic figures and basic strumming patterns through having things professionally written in standard rhythmic notation, and encouraging a little bit of sight singing, or call and response singing, in every lesson.