I think your problem resides on how to show the data. This link to data-to-viz has a diagram that might help you identify the best plot for your students and how each one of them sums up their contributions to the whole.

Data-to-Viz

And this other web link might help you to find a use-case similar to yours.

Betterfigures

I think your problem resides on how to show the data. This link to data-to-viz has a diagram that might help you identify the best plot for your students and how each one of them sums up their contributions to the whole.

I think you should use an histogram that shows the prev years and how each group or budget allocation changes over the time. There are some ranking that will help you make the graph easy to read and those are:

#1 Position in a common scale #2 Position in a non aligned scale #3 Length, Direction and Angle #4 Area #5 Curvature, Volume #6 Shadding and Color saturation

"Cleveland & McGill (1984)"

Example:

I'll keep the links for more reference.

Data-to-Viz , Betterfigures