Commander Xia wasn't against his son dating a high school student. Why did he need to oppose them? The lady hadn't even liked his son! As long as the lady didn't agree, it was just a one-sided love.
But, he had to look into the lady too. He didn't need a daughter-in-law with a powerful background but he had to ensure that the character of his daughter-in-law was good.
"Don't bring the lady to me first. I don't want to know what's happening between the two of you either. She's still a high school student. You're at least six years older than her. If you really like her, the least you can do is to not disturb her now."