What position does Dave's mother force him to do while the rest of the family eats?

David's mother forces him to "stand" in the basement while the family eats dinner.

When I returned to the house from school, I immediately accomplished the various chores Mother assigned me. When the chores were finished, I went directly to the basement, where I stood until summoned to clean off the dinner table and wash the dishes. It was made very clear that getting caught sitting or lying down in the basement would bring dire consequences. I had become Mother’s slave.