First; Really nice to see application coding introduced. Overall, a nice project for demonstration purposes.
Issues;
(1) The article code didn't Dim the NextRow variable - not a deadly sin, just good practice.
(2) Haven't looked back to prior versions of Excel VB toolbox, but, the "Option" control may be a better choice over the "Checkbox" control, since code only enters the highest value no matter how many check boxes are marked.
(3) Looks like the second, "Application.WorksheetFunction.CountA(Range("A:A")) +1" line was an attempt to correct the line above, adding the period in place of the space. Only problem is it didn't assign the value to NextRow.
(4) UserForm1 fields need some basic validation as it is possible to enter an Education level without a name and the next entry from the user form will fall into the same place, possible overwriting whatever level was placed in the worksheet.
(5) Would also be a good place to discuss the typical and necessary Macro Security settings and how a user may interpret the initial warning dialog that appears when the file is loaded with Medium security.
Overall, a fun and interesting demonstration.