My oldest and I were working the same place when he got his first paycheck. He was totally flabbergasted when it was less than he’d calculated he’d be getting.
He had anticipated income taxed but was not prepared for Social Security and Medicare.
I explained SS to him like this: that amount there? That is being taken from your check and being put directly into your grandparents’ SS checks. There is NOT an account with your name on it, set aside for you and waiting somewhere until you retire. From time to time you’ll get a letter from Social Security telling you how much “you” have available. That’s imaginary, OK?
A coworker and I had not long before that about the same subject. He had been looking at what he had been paying in SS as some sort of retirement account. We disabused him of that notion. He was a lot older than my kid, too!