Albus believes that his father, Harry, seems to be dismayed that he ended up in Slytherin House.
Harry says to Albus quite pointedly that he would be proud of him if that did in fact happen:
“Albus Severus,” ... “you were named for two headmasters
of Hogwarts. One of them was a Slytherin and he was probably
the bravest man I ever knew.”
“But just ...