Students might not be aware of the time horizons of applications for opportunities. Oftentimes, these things need more advance planning than expected.
Here I suggest timelines for undergraduates doing research and applying to grad school, particularly within the United States. Please make sure that students working with you are aware of these deadlines.
Applying to graduate school
You should be deep into grad school applications at the start of the Fall, one year before you plan to start grad school.