My son is in his senior year at UCSB
He does not want to go back had a very bad year last school year. He wants to stay at home and finish at
A cal state can he do that.
He would need to check with any Cal state that he wants to attend to make sure they have room for a Senior level transfer. If he wants to attend a CSU this Fall 2019, the application deadline was November 30 2018 and acceptances have been completed since this past Spring 2019. He could take a Gap semester and apply now for Spring 2020 at the Cal States that offer Spring transfer spots. The Spring 2020 application is open until August 31, so he better hurry.
I’d explore it with the CSU directly - make an appointment with an admissions advisor and see what they recommend about admission and how it will impact his graduation timing.