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Professor Teertstra has some evaluation criteria, but we’d like to do the filtering internally to ensure all our co-ops get a great experience!
Being an upper year helps significantly in this because it ensures you have some technical expertise. Having this technical expertise is important so you can have some pieces of knowledge to pass along to your co-op student. Having strong co-op experiences (i.e. Cali) is also useful in supplementing this because you have seen how some tech companies operate so you can teach your co-op student those best practices.
Historically co-op managers should be 3A or above unless they strongly satisfy the above criteria. Someone with technical experience is key for mentorship, a hint of managerial experience is key for tasks.