With the effort you have gone to to normalise your data, I dont think that the laziness of rewriting your data each time is good laziness. It could indeed be dangerous - because a user could accidentally change the data on the form and submit an error.
By rearranging your form so that people input changes only, perhaps by using a dropdown to select the old name and new qualification, or a text box to enter a new name and a new qualification.
If you are using SQL then you could update it will an UPDATE query something like
If you are manually implementing your own database with text files, you will probably have to rewrite the file each time, though you could perhaps just append a line each time - thus allowing you to undo changes easily.