Teens showering in Halloween masks

I saw this American movie on TV in the 1980s. It was about a lonely rich boy living in a big house with a domineering mother. The kid has no friends and is completely obsessed with horror movies. He meets this poor girl from the wrong side of the tracks and they become friends against his mother’s wishes. I vividly recall the scene where they are dancing in the shower in their underwear while wearing monster masks and the mother walks in and freaks out. That’s all the info I have.