Armstrong says she complained to her supervisor, and David stopped eating with the teacher.
But when a review of David's education plan came up and Houston wanted Armstrong present, Armstrong believes she was punished for her complaint. Armstrong said her bosses told her to call in sick that day.
She later learned that his education plan included learning hygiene, how to write down his name and phone number in case he ever gets lost, and how to communicate more words with his iPad, Armstrong said. There was nothing in it about table manners.
Armstrong said she learned more about the school's attitude toward David when an administrator expressed doubts that David could actually express himself with the iPad at all.
"He knows what we're saying right now," Armstrong said, speaking to ABCNews.com on the phone in the same room as David while his brother looked after him. "He's just not verbal."
Someone at the school eventually broke David's iPad by forcing him to leave it out in the rain for fear that he was bringing a recording device into the classroom, Houston said.
"They don't like her and they don't like him," Armstrong said.
The incident last year that most upset Armstrong, however, was a simple class party in which the teacher brought cupcakes for every student in the class.
Every student, that is, except for David, she says.
Not realizing that the teacher hadn't brought him one, Armstrong asked David if he wanted a cupcake, and he answered "yes" on the iPad. The teacher then said she wouldn't give David one because of his diabetes. Armstrong says she reminded the teacher that all she had to do was adjust his insulin levels, and he could eat it.
"I can even tell you what color he'll choose: red. If there's no red, orange," Armstrong said. "I always have tried to … advocate for David and just try to get through the day. Why do we have to make the kid so upset that he pukes on his shoes?"
The district had sent Houston a previous settlement agreement letter in June for $50,000, which she told ABCNews.com she rejected before she sent David back to school this month.
Bogard said Houston's lawyer didn't reject the first settlement agreement as Houston claims. Instead, Houston's lawyer responded with a counter offer asking for more money.
Houston said she did not authorize her lawyer to submit a counter offer. The lawyer, who has since quit, sent the district an itemized list to explain why the $50,000 wouldn't cover the costs of David's education, Houston said. She said it was a rejection, not a counter offer.
"Any offer made was part of ongoing confidential settlement discussions in which David's counsel fully participated," Bogard said in a prepared statement on behalf of the district. "The settlement offers that Ms. Houston refers to are no longer valid."
Bogard said the district denied any wrongdoing, but said she couldn't comment further, citing pending litigation.