Eight-year old Ishaan Nandkishore Awasthi dislikes school and fails every test or exam. He finds all subjects difficult, and is belittled and berated by his teachers and classmates. However, Ishaan's internal world is full of wonders that he is unable to convey to others, magical lands filled with colour and animated animals. He is also an artist whose talent is unrecognised.

Ishaan's father, Nandkishore Awasthi, is a successful executive who expects his children to excel. Ishaan's mother, housewife Maya Awasthi, is frustrated by her inability to educate her son. Ishaan's elder brother, Yohaan, is an exemplary scholar and athlete, which Ishaan is frequently reminded of.

After receiving a particularly poor academic report, Ishaan's parents send him to a boarding school. There he sinks into a state of fear and depression, despite being befriended by Rajan Damodharan, a physically disabled boy and one of the top students in the class. He even contemplates suicide by climbing up the fence in a terrace, which Rajan manages to save him from.

Ishaan's situation changes when a new art teacher, Ram Shankar Nikumbh, joins the school's faculty. An instructor at the Tulips School for young children with developmental disabilities, Nikumbh's teaching style is markedly different from that of his strict predecessor, and he quickly observes that Ishaan is unhappy and contributes little to class activities. He reviews Ishaan's work and concludes that his academic shortcomings are indicative of dyslexia.

On his day off, Nikumbh sets off to Mumbai, to visit Ishaan's parents. Nikumbh is surprised to learn that Ishaan is passionate about painting, and shows great talent in art. Nikumbh then asks Awasthi as to why he sent Ishaan to a boarding school. Awasthi replies that Ishaan was an ill-mannered boy and was a poor student. Nikumbh shows Ishaan's mother her son's notebooks and gives an analysis of the script. Nikumbh deduces that Ishaan has severe difficulty in understanding letters and words. Awasthi tries to dismiss it as a mere excuse for Ishaan's laziness. Nikumbh demonstrates what Ishaan experiences every day at school. He states that Ishaan has dyslexia as well as he may be having other conditions, which make him a difficult child.

Still unsatisfied with Nikumbh's interpretation, Awasthi bluntly dismisses Ishaan's disability as mental retardation, which frustrates Nikumbh, who criticises Awasthi for his crude and inaccurate explanation of Ishaan's condition. Nikumbh argues that Ishaan is an above-average child whose condition suppresses his artistic and mental talent, leading Awasthi to feel regret for his treatment of Ishaan.

Nikumbh returns, and subsequently brings up the topic of dyslexia in class, and offers a list of famous people who were dyslexic. Later, Nikumbh reveals to Ishaan, that he too is a dyslexic and faced problems similar to Ishaan. Nikumbh then visits the school's principal and obtains his permission to become Ishaan's tutor. He attempts to improve Ishaan's reading and writing by using remedial techniques developed by dyslexia specialists; Ishaan soon develops an interest in language and mathematics, and his grades improve.

Towards the end of the school year, Nikumbh organises an art fair for the staff and students. The competition is judged by artist Lalita Lajmi. Ishaan, with his strikingly creative style, is declared the winner and Nikumbh, who paints Ishaan's portrait, the runner-up. The principal announces that Nikumbh has been hired as the school's permanent art teacher. When Ishaan's parents meet his teachers on the last day of school they are left speechless by the transformation they see in him. Overcome with emotion, Ishaan's father thanks Nikumbh. As Ishaan gets into the car to leave with his parents for summer vacations, he turns around and runs toward Nikumbh, who gives him a hug and tells him to return next year.

• Darsheel Safary as Ishaan Nandkishore Awasthi: In looking for an actor to play the central figure of Ishaan, writer Amole Gupte turned to Shiamak Davar's Summer Funk workshops. Gupte had several boys informally audition by explaining to him how they would react to scripted situations from the film. Of his decision to cast Darsheel Safary, Gupte recalls that "it was a tough call. But Darsheel has the mischief in his eyes to be Ishaan. Everyone just naturally gravitated towards him."
• Aamir Khan as Ram Shankar Nikumbh: Gupte, who based the character on his art teacher Ramdas Sampat Nikumbh, initially asked Akshaye Khanna to play the role.
• Tanay Chheda as Rajan Damodran: Ishaan's classmate at New Era High School.
• Sachet Engineer as Yohaan Nandkishore Awasthi ("Dada"): Ishaan's elder brother.
• Tisca Chopra as Maya Awasthi ("Maa"): Ishaan's mother, who gave up her career to raise her children. Chopra tended to speak softly during filming and was subsequently required to re-record some scenes using automated dialogue replacement.
• Vipin Sharma as Nandkishore Awasthi ("Papa"): Ishaan's "strict, hard, dominating father". Part of the reason for Sharma's casting was his "extremely strong and dominating" face that "exudes harshness." Described by Khan as "naturally polite" and sensitive, Sharma was instructed to lower his voice to sound "harsh" and "dominating".
• Girija Oak as Jabeen, Nikumbh's co-worker
• Bugs Bhargava and Shankar Sachdev as Sen Sir and Tiwari Sir: Two teachers at New Era High School, whose attitude towards Ishaan softens as his grades improve and he wins the art contest. The roles are caricatures of teachers in general.
• M. K. Raina as the principal of New Era High School.
• Lalita Lajmi as herself in a cameo role. It was her first appearance as an actor.

Development

The husband and wife team of Amole Gupte and Deepa Bhatia developed the story that would eventually become Taare Zameen Par as a way of understanding why some children cannot conform to a conventional educational system. Their initial work began as a short story that evolved into a screenplay over seven years. Deepa Bhatia later stated in an interview with The Hindu that her original inspiration was not dyslexia but rather the childhood of Japanese filmmaker Akira Kurosawa, who performed poorly in school. Her goal was thus to explore the story of "a child who did not fit into the school stream." She referenced a specific moment in Kurosawa's biography where he began to excel after meeting an attentive art teacher, and noted that this scene "became the inspiration for how a teacher could transform the life of a student".

In developing the character of a young boy based on Kurosawa, Bhatia and Gupte explored some possible reasons why he failed in school. Their research led them to groups such as the Maharashtra Dyslexia Association and Parents for a Better Curriculum for the Child (PACE). Dyslexia eventually became the central topic and theme of the film. The pair worked with dyslexic children to research and develop the screenplay, basing characters and situations on their observations. Bhatia and Gupte carefully concealed the children's identities in the final version of the script.

Khan and Gupte first met in college. Khan has said that he admired Gupte's abilities as an actor, writer, and painter. Three years before the film's release Gupte brought Khan to the project as a producer and actor. Gupte himself was to direct, but the first week's dailies were a great disappointment to Khan, who "lost faith in Amol and his capability of translating on screen what he had so beautifully written on paper". Khan was on the verge of withdrawing his participation in the film because of these "creative differences", but Gupte kept him onboard by stepping down as director. Contrary to Khan's claim, Gupte lashed out saying that after the wrap-up party, Khan announced that he was the director of the film, despite Gupte acting as director. Had it been necessary to hire a third party, production would have been postponed for 6–8 months as the new director prepared for the film. Keen to keep Safary as Ishaan—the actor might have aged too much for the part had production been delayed—Khan took over the role of director. Taare Zameen Par was Khan's first experience in the dual role of actor and director. He has admitted that the transition was challenging, stating that while he had always wanted to direct a film, it was unknown territory for him. Gupte remained on set, "guiding and, at times, even correcting ".

Title and translation

Initially the film was to retain the short story's title of "High Jump", because of Ishaan's inability to achieve the high jump in gym class. This subplot—filmed but later cut—tied into the original ending for the movie. In this rendition, a "ghost image" separates from Ishaan after the art competition and runs to the sports field; the film would end on a freeze frame of Ishaan successfully making the leap. Khan, however, was unhappy with that proposed ending and convinced Gupte to rewrite it.

With the working title no longer relevant, Khan, Gupte, and Bhatia discussed several alternatives, eventually deciding on Taare Zameen Par. Possible translations of this title include Stars on the Ground and Stars on Earth. According to Khan:

Taare Zameen Par is a film about children and it is a film which celebrates the abilities of children. Taare Zameen Par is a title which denotes that aspect. It is a title with a very positive feel to it. All the kids are