I still pay CSA as son is still in education but he rarely attends

I get £320 a month taken out of my wage I wouldn’t mined but my son is nearly 18. The collage let him take crap courses that wont give him anything he can use and I have to pay his wages for it. He has done the same course for two years and intends to take the same course next year. He doesn’t even turn up to collage half the time. I started work the day I left school nobody paid for me until I was 20. It’s a joke and makes me resent him a little.