I can’t find any record of a Mississippi Supreme Court decision regarding a program like you described. I did find evidence that Mississippi actively permits dual enrollment for secondary and post secondary education. Do you have a source for the decision you referenced?
he didn't say it went to the Supreme Court or even any Mississippi court
he said it was dismantled. teacher's unions and their political allies and pliant schoolboards are always vehemently opposed to any programs like this. something that shows some students excelling and or makes some teachers look good just makes other teachers look bad, and that raises questions and increases scrutiny from outside, and they can't allow that.
https://law.justia.com/codes/mississippi/title-37/chapter-15...