Which values to assign to a quantified dummy variable
It's generally not good practice to go from categorical/dummy variables to quantitative variables, as csilvia noted, because categorical/dummy variables have less information than their quantitative analogs. None of the variables in your dataset are quantitative except for math, reading, writing, and total, which I'm assuming are outcomes of interest, not inputs.
If your teacher wants you to include quantitative variables, I'd go back to the original dataset and see if there's anything quantitative included there rather than trying to make a categorical variable fit as a quantitative one.