Not in the CREATION of the work, but there are laws that restrict an adult's exposure of his or her naked body to a minor. This also applies to any adult that provides "pornographic" content to a minor, so even photographs could be a problem.. There are obvious exceptions made to the law, such as when a family practices social nudity at a naturist camp or other social event. This same kind of exception may apply to a parent supervising a session where a nude model is present for a student to practice live drawing.
The line between what might be an acceptable, legal practice and what the law might consider a form of child abuse could depend on the actual context of the drawing session and how it's presented and chaperoned, and, simply, whether or not one gets caught by the authorities.
Consider the case of the mother who took pictures of her two toddlers in the bathtub. She took the film to a local processor who prompty called the police. The mother was charged with producing "chld pornography." The charge was eventually dismissed, but it goes to show how sensitive some of us in society have become.
A "safer" alternative would be to present models wearing skimpy bathing suits, even as brief as a thong, and "pasties" on the breasts. If the model was wearing, at least, as much as might be acceptable on a public beach, it would satisfy any legal restrictions, without spoiling the practice benefits of live figure study drawing.