watershed

"The watershed between the two school districts runs along the highest peak of the mountain range. "

"The rain that falls on the mountain all flows into the river because the mountain is part of the river's watershed. "

"The new teacher's arrival was a watershed moment for the struggling class; after that, student engagement dramatically increased. "

"The watershed for the local radio station came when they switched to a later evening time slot, allowing for more mature content. "

"The new teacher's arrival was a watershed moment for the struggling class, marking a significant improvement in student engagement. "