First off, Aamir Khan deserves credit for trying to shed light on what I'm sure is a problem in India. As it was when I saw 3 Idiots and had to take the movie's word for it about the problems with suicides, I had to also take it that in this case, Like Stars on Earth, there's no real perception from teachers about dyslexia and other cognitive disorders (the young boy in this story, Ishaan, played by Safary, is this kid, and I have to wonder if he also had un-diagnosed ADD and/or aspergers, the latter being more about social awkwardness which Ishaan also is). In the United States its something that gets tackled when kids are very young in schools - and, of course, even in the lamest public schools there's a guidance counselor of some sort, which seems to be a deficiency in the schools depicted here - so I can understand why it would be something to shine a light on. And, as a first time director, Khan is very good at drawing out (mostly) strong performances from his actors, even if they only have a few minutes of screen time.
I know you're waiting for the 'but' with all this (hence why it's a 6/10 and not higher, as I was hoping for), however I'll give some praise before I get to that. The first hour or so of this movie is actually quite compelling; there's only one or maybe two musical sequences, though they don't really POP out the way that other Bollywood movies seem to (there's one sequence, where we follow Ishaan as he wanders the city in a daze as he cuts classes, unsure what to do with himself, and it is actually very interesting just in the little details of what he comes across are striking). There's melodrama, but it unfolds as a character study first and foremost.
It's a simple enough set-up, and I think the idea is that many in the audience could or will be able to actually identify with Ishaan: he's the day-dreamer, staring out the window in class, and not necessarily always fitting in with what's expected. He doesn't have what US kids might have like, say, Ritalin or other drugs to pump up for attention. His imagination is much freer than that, and the child actor playing him is a joy to watch, whether he's being cheeky or angry or glaring or really having to pull out the water-works, which is what happens especially when he is sent off by his (to say the least) uptight father to boarding school.
Where the movie kind of gets into being not as strong is ironically with the (first time) director and other star: Aamir Khan. He is wonderful as far as the writing lets him be, which is kind of like as the perfect, super-open-minded type of teacher and bursts into the film almost like some wild and crazy clown for his students. It's also the one truly obnoxious Bollywood-musical type of number, though made somewhat interesting by Ishaan being quiet/depressed at his desk. It's from here that Like Stars on Earth hits its message home like a sledgehammer - which is frustrating since Khan is still delivering very well as an actor, and it's kind of heartwarming to see a kid really start to learn and grow (which is not unexpected, you can see the plot a mile away).
But there's a lot of moralizing and preaching in the second half that, while always with the best of intentions, drowns out some of the stronger, simpler drama that was unfolding in the first hour/sort of the first half of the movie, where we also got to see more variety in Safary's performance. After a certain point he just becomes a sobbing/catatonic mess, or a cheerful-happy sort of guy, and worst is his father who is so one-note until he grows one other note and sticks with that (the Parent-Who-Won't-Understand-Until-It's-Jammed-Down-His-Throat cliché, which exists I'm sure).
Some of the music varies between tolerable (the guitar stuff as the giant, climactic painting event at the school is decent) and not so tolerable (you'll know it when you hear it). And lastly, I thought the reveal of Ishaan being a genius painter came slightly out of nowhere; we see a flip-book at one point, but not much else. It would be one thing if Khan showed the kid painting and no one recognizing it, but the first half is so front-loaded with the pain of not-recognizing letters and numbers that the art element comes as a surprise come midway through the movie.
I wrestled with what I would give the movie, and in a way I give it a very slight recommendation, and if you know you love "feel-good" movies that ultimately deliver a strong, heart-felt message, have at it. But it's too long by at least half an hour/45 minutes for my own taste (and I know I might not "get" Bollywood, but this wasn't really as wild and crazy as a lot of them so the length wasn't as justified for the excessive musical numbers and so on), and there's wasted potential with what is deep down a very powerful message about education and understanding disabilities in a rational way.