The movie starts with an alien ship. After the boy and the alien become friends, the boy takes advantage of the alien's skills. For example, while swimming, the alien sticks to his back and helps him swim fast. The alien also writes his homework and does this kind of stuff for him.
I think LSemi has the right answer. Chocky, John Wyndham, is a 1963 novelette expanding to a 1968 novel, about a boy with an alien in his head that helps him out.
David Gore becomes concerned that his twelve-year-old son, Matthew, is too old to have an imaginary friend. His concerns deepen as Matthew becomes increasingly distressed and blames it on arguments with this unseen companion, whom he calls "Chocky". As the story unfolds, it becomes clear that the friend is far from imaginary, but is an alien consciousness communicating with Matthew's mind — a fact that is of interest to shadowy government forces.
It does aid him with his homework and helps him swim as per this review.
Things get worse when Chocky shows that she can take over Matthew’s body as well as his mind. She can paint with his fingers, swim using his arms and legs—she uses this capability to save both Matthew and his sister from drowning, thus attracting the attention of the press and starting a “guardian angel” rumor. And, finally, she can talk through his mouth, thus communicating directly with the narrator while Matthew is in a sort of mediumistic trance. She has come to say goodbye, because her presence has attracted undue attention to Matthew, and the powers that be want to get hold of Chocky and her superior scientific knowledge.
And, as noted, there were three TV presentations of it, each six episodes.
It does start with an alien ship landing (although it's shown to be a film that Matthew and his family are watching). Chocky does not visually manifest itself, although unlike the book, Chocky communicates in their own voice rather than just being a voice in Matthew's head.