The short answer is that it depends on the specific education requirements applicable to the social workers in the particular situation. 

One court has ruled that social workers are not exempt from overtime pay requirements. In Solis v. State of Washington DSHS, No 10-35590 (9th Cir., 9/9/11), the court ruled that social workers in the State of Washington were not exempt from overtime because the "learned professional" exemption was not applicable.  There was a degree requirement for the Washington social workers but the court ruled that it was not specific enough for the social workers to be exempt from overtime pay requirements. You can read more about the decision on the Kentucky Employment Law Blog.   

Whether social workers elsewhere are exempt from overtime because they meet the "learned professional" exemption requirements may very well prove to be the case. It is a question that an exeperienced overtime lawyer should review. This question like many others having to do with exemptions from overtime pay requirements is very fact-specific to each individual situation.