HORSE film - Lassie Storyline - ANYONE??

Really hopeing someone can help!

I remember years and years ago i watch a film , it had a black horse in and was the lassie storyline - had a young girl in it , her family kept selling the horse only for it to run back to them , the horse used to pick her up at school etc - does anyone have any memory of this??

Am sure it was totally the Lassie storyline but was so many years ago i can only remember bits! Have a feeling the family where broke as they needed to rain rain for the crops to grow and at the end of the film it rains.

Thanks! x