Wont let me update the database. need help.

[Sirkssim]

I'm actually working on a project for school (no I'm not actually asking you do to it for me) Just trying to see what I am doing wrong...

Microsoft VB Grade Book. A teacher maintains a database containing two tables-student and grades. The students table has three fields: studentID, lastName, and firstName. The Grades table has four fields: studentID, firstExam, secondExam, and finalExam. At the beginning of the semester, the Students table is filled in completely with a record for each student in a class, and the Grades table has a record for each student that contains only the students ID number. (Note: The database is contained in the file Gradebook.accdb from the folder CH10 Databases.) Write a program that allows the instructor to record and process the grades for the semester. The program should do the following:

A) Use a navigation toolbar to fill the Grades table.

B) After all the grades have been entered, display a DataGridView control showing the name of each student and his or her semester average. The semester average should be calculated as (firstExam + secondExam + 2*finalExam) 4.

I am attaching pictures of the form that I have created (everything is binded properly i believe) For some reason it is not letting me update the database. The second one is the error I am getting. I have no idea what is going wrong. I have spent hours trying to figure it out and can't. Any help or direction is VERY appreciated.

[Sirkssim]

I'm not even sure if that is the problem. The first Student ID the Aj-123456 is the only one that shows up when I click through. I don't know if they are supposed to all be showing up or not when i click the next arrow in the binding navigator.