Is Rafael nodding off? Does Sarah tend to put her head on her desk? You can find all sorts of advice to deal with the problem of sleepyheads.
Calling home to alert parents may help. Maybe Rafael has been playing computer games all night. Maybe Sarah has been texting friends or trying to defeat Rafael in his virtual quest. Electronics create many drowsy, sluggish students nowadays. Lack of food can sometimes be a factor. Some kids just have trouble waking up. An ample amount of research shows we are starting school before many of our students come to full consciousness.
In any case, I practice my operatic voice on these students. Make a joyful noise. Or make a loud, operatic noise anyway. Make it up as you go.
“Rafael, you are sleeping again. Oh, Rafael, you cannot sleep. You must wake up, wake up, wake up. Oh, Rafael, sleeping in class is bad. You cannot sleep, you silly lad. Tra la la” Etc.
The kids will laugh and if your voice is as bad as mine, I guarantee Rafael will be up and begging for mercy pretty quickly.