Slot washers are great (and preferred) for fine art and single users but typically won't be able to handle the demands of a gang darkroom, where everything needs to get washed quickly and ready for the next class/session. The OP probably needs something
automatic and higher volume. If cost is an issue (and when isn't it), I suspect a horizontal overflow washer might be sufficient (like my
RC/"prewash" left side of sink), if you can enlist students to keep their own prints moving in the washer from time to time. These have no moving parts to wear out and are otherwise perfectly suitable for many RC prints (non-archival washes). Going out on a limb here, repairs to your existing washer might be easier than you think.