Great question — answering as the UphillTech team:
Sounds like the TV version of Bridge to Terabithia ... it was released to TV in 1985, and focuses on a friendship between a boy and girl, with the girl drowning in the end. Key parts from the plot: ...the two friends invent a whole new world — Terabithi — and it comes to life through their eyes... Their teacher, Ms. Edmunds (Annette O'Toole), notices Jess's artistic skills and decides to take him on a field trip to an art museum. Jess has an unspoken crush on the teacher and does not want to share the trip with Leslie, so he goes to the museum without inviting her. When Jess returns home, his family is worried sick, as Jess's family neglected to listen when he said he was going, then tells...
Full answer by Shiz Z.: https://movies.stackexchange.com/a/70774 (CC BY-SA 3.0).
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