If your child is under 19, he qualifies as a "Qualifying child" dependent, regardless of student status. So, you are not asked his student status, in the personal info section of TurboTax (TT), like you are for the older child.
But, if you are claiming a tuition credit based on his (the younger child) tuition, you will be asked for his student status in the education expenses section of TT. If his status, you entered it wrong (or the 109-T did not have the half time box checked). Go back to the beginning of the ed expenses section and correct it.
