If coeducation is a means of education of both sexes without concept of veil(pardah), Islam certainly prohibits it as the very purpose of education is hampered by sensual instincts_thanks to research in psycho dynamics.

However if the source of education is common but there is a segregation(pardah) on the basis of sex then such a coeducation is beneficial rather than harmful.e.g a speaker addressing to university students in a hall with separate seating arrangement for girls and boys.

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"Our greatest glory lies not in never falling,but in rising every time we fall": Confucius