Secret Admirer (1985) on Netflix

Secret Admirer is the story of teenager Michael Ryan, who receives a passionate anonymous love letter on the last day of school. Michael's long-time friend Toni has a friend, Deborah Anne Fimple, who Michael is constantly obsessed with. Later that day, Michael and his friends get together at his house. One of his friends, Roger Despard, gets hold of the letter and reads it out aloud, surprising everybody. Because Michael is totally smitten with Deborah Anne Fimple, Roger easily convinces him that she must be the girl that wrote him the letter. Later that night, Michael meets her at a party, and begins smooth-talking her, by repeating the words of the love letter. Because Deborah Anne Fimple does not respond to Michael in the way that he expected, he soon realizes that she did not write him the letter. After the party, Michael and Toni walk to a quiet spot and lie down on the grass. Michael explains to Toni how he made a fool of himself in front of Deborah Anne Fimple, and how much he loved the letter. Toni then convinces Michael to write an anonymous love letter to Deborah Anne Fimple. Michael ends up writing two letters, but Toni re-writes them before passing them on, and without telling Michael. Consequently, all the letters fall into the wrong hands, causing confusion with almost everyone in Michael's life, until finally he discovers who wrote him the love letter.