A lot of charting is arranging the data in the spreadsheet. The arrangement you show (a flat list) is good for database work, but does not work very well for charting. The goal is to rearrange the data so that you get something like:
The first two methods for rearranging the data that come to mind:
1) A pivot table (https://www.excel-easy.com/data-****...ot-tables.html ) where you have day as row label, student as column label, and sum of score as the pivot values. A line chart like what your picture shows would be straightforward from the pivot table data, but a scatter chart is not an allowed pivot chart type. If you decide you need a scatter chart instead of a line chart, then you can follow instructions here: https://peltiertech.com/regular-char...-pivot-tables/
2) A "conditional formatting" technique like this: https://peltiertech.com/conditional-...-excel-charts/ where you add helper columns to the right of the data with each name at the top, then use an IF() formula to make a copy of the data under the appropriate student name. Use these helper columns in your line/scatter chart.
Which approach do you like? Where do you get stuck in implementation?