Official Mark Column is a hard coded column that cannot be removed. However, it is a column that can be locked and greyed out so teachers can't enter marks. 

Setup>Marks and comments>Lock/unlock terms

Click on the term to lock or unlock the term

When teachers log into connectED they will see the official mark column but as you can see the mark column is greyed out.

In this example we are using the first reporting period/ progress reports. Teachers can click on the cog wheel and unselect show final mark.

Any term other than the last term will show the official marks column in connectED, as long as the final mark/ Term  is locked teachers can't add marks.