Get the Average from Date from Checkboxes

I am trying to put together a sheet for tracking student scores based on criteria. I have made checkboxes (that work!) that when checked, give the averages of criteria. 

My next step is to make a formula that will gather all same criteria as the row in the checkbox and average them from that point. 

I have the formula that will get the minimum date and the matching criteria to that date. From here I need to figure out how to get the average of all criteria in a date greater than the date from the box that is checked.

Add a Label to Chart Data

I created a chart from some data. Gridlines would definitely help to make it easier to read, but a label would be even better. 

To add a label, go into the chart editor and click on Customize in the top menu. Then scroll down to Series. In the Series menu towards the bottom are three checkboxes - the last one is Data labels. You might need to change the format. 

Click on the drop down menu and select from source data.