There was a movie I recall watching that had couple of older kids (high school aged) leading a younger group of students trying to avoid being captured by couple of bad men (or possibly one bad man). They were in a schoolhouse (old fashioned type) but set in that present time era (1980’s or 1990’s) in the countryside. The bad men attempted to take them hostage - they killed their teacher (I think). They escaped by going into the woods and took a long route trying to escape their pursuers… I recall that they had to swim under water to bypass a huge rock/boulder to get to another side, and the pressure was so bad because the bad guys were nearby and nearly shot one of the students. The bad men ended up being killed by the students, but one of their hearts ended up in a jar in the end of the movie. A female older student looks at that jar to reflect and then she proceeds to read a story to younger students; the end credits begin. I cannot for the life of me remember what the name of the movie was!

I believe that this is the Australian movie Fortress with Rachel Ward (not to be confused with the Christopher Lambert prison epic of the same name).