Location: I'm the uber Spaminator !
Then you need to tell the db which row you want to update:
set field1='x', field2='y', field3='z'
So, you design a screen where the teacher can edit each fields.
When the page is acessed, you get the student id from the url, do a SELECT query to load it's values, and display them in each fields of the page form.
When the teacher click the submit button, your target page extract the values from the POST (with the student id), and send the UPDATE query like up there.
Only a biker knows why a dog sticks his head out the window.