Is sending food to students' families—some of whom are well-off and others not—considered feeding the hungry?

Feeding people is a religiously encouraged act, and it includes both the poor and the rich, whether it is charity, a gift, or hospitality. The proof of its virtue is the Prophet's (peace and blessings be upon him) saying: "O people, spread peace, feed people, uphold ties of kinship, and pray at night while people are asleep, and you will enter Paradise in peace." Feeding the needy is charity, and feeding the non-needy is an act of kindness.