Being "disrespectful to" people includes calling them names, being rude to them, not listening to what they're saying, and so on.
You can't expect to be disrespectful to your teachers and still be rewarded with good grades and recommendations.
Another preposition that you can use after "disrespectful" is "toward":
She was disrespectful toward me and my entire family.
You can also use the word "disrespectful" by itself:
There's no need to be disrespectful!