If you are already reading the content as a stream you can do the following:
myObject scp = null;
XmlSerializer serializer = new XmlSerializer(typeof(myObject);
using (Stream stream = request.Content.ReadAsStreamAsync().Result)
{
scp = serializer.Deserialize(stream);
}
Edit:
The reason you are getting the error is because the XmlSerializer is expecting an xml declaration tag. If your xml does not contain this you can define the root attribute like below:
XmlSerializer serializer = new XmlSerializer(typeof(myObject), new XmlRootAttribute("Student"));