It depends on the hospital. I'm starting medical school in the fall and worked as a Therapeutic Assistant (essentially equivalent of psych tech) on an inpatient unit for the past 1.5 yrs. They required a bachelor's degree and some prior experience working with kids (I worked on the C&A floor, sure tat wouldn't be needed for other units).
It was overall an awesome experience, I recommend it. You'll learn a lot, see some extremely interesting cases and it's a great chance to network with psychiatrists on the unit.