Postback occurs when client side validation is enabled MVC3 - asp.net-mvc-3

Question

I have client side validation enabled and indeed it is working in that I see error message for required fields when I submit the form. But a postback is also occuring despite the fact that client side validation has fired. It is my understanding that client side validation is supposed to suppress the postback. Can someone confirm for me that is the expected behaviour and see if there is anything amiss with this view. Many thanks.
This is the view in question
#model Intranet.ViewModels.Student.CreateStudentViewModel
#{
ViewBag.Title = "Create Student";
}
<h2>
Create Student</h2>
<script src="#Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="#Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>
#using (Html.BeginForm())
{
#Html.ValidationSummary(true)
<table class="detailViewTable">
<tr>
<td>#Html.LabelFor(c=>c.Contact.Title)</td>
<td>#Html.EditorFor(c=>c.Contact.Title)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.Title)</td>
</tr>
<tr>
<td>#Html.LabelFor(c=>c.Contact.FirstName)</td>
<td>#Html.EditorFor(c=>c.Contact.FirstName)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.FirstName)</td>
</tr>
<tr>
<td>#Html.LabelFor(c=>c.Contact.LastName)</td>
<td>#Html.EditorFor(c=>c.Contact.LastName)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.LastName)</td>
</tr>
<tr>
<td>#Html.LabelFor(c=>c.Contact.Phone)</td>
<td>#Html.EditorFor(c=>c.Contact.Phone)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.Phone)</td>
</tr>
<tr>
<td>#Html.LabelFor(c=>c.Contact.AltPhone)</td>
<td>#Html.EditorFor(c=>c.Contact.AltPhone)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.AltPhone)</td>
</tr>
<tr>
<td>#Html.LabelFor(c=>c.Contact.Email)</td>
<td>#Html.EditorFor(c=>c.Contact.Email)</td>
<td>#Html.ValidationMessageFor(c=>c.Contact.Email)</td>
</tr>
<tr>
<td>Guardian 1</td>
<td>#Html.DropDownListFor(c=>c.Guardian1ID, new SelectList(Model.Contacts, "ID", "FullName"))</td>
</tr>
<tr>
<td>Guardian 2</td>
<td>#Html.DropDownListFor(c=>c.Guardian2ID, new SelectList(Model.Contacts, "ID", "FullName"))</td>
</tr>
</table>
<p>
<input type="submit" value="Create" />
</p>
}
<div>
#Html.ActionLink("Back to List", "List")
</div>
And here is the CreateStudentViewModel
public class CreateStudentViewModel
{
public int ID { get; set; }
public ContactViewModel Contact { get; set; }
public int Guardian1ID { get; set; }
public int Guardian2ID { get; set; }
public List<ContactViewModel> Contacts { get; set; }
}
And the ContactViewModel that contains the validation properties.
public class ContactViewModel
{
public int ID { get; set; }
[Required(ErrorMessage = "Title is required")]
public string Title { get; set; }
[Required(ErrorMessage = "First Name is required")]
[DisplayName("First Name")]
public string FirstName { get; set; }
[Required(ErrorMessage = "Last Name is required")]
[DisplayName("Last Name")]
public string LastName { get; set; }
public string Phone { get; set; }
[DisplayName("Alternate Phone")]
public string AltPhone { get; set; }
public string Email { get; set; }
public string FullName
{
get { return string.Format("{0} {1} {2}", Title, FirstName, LastName); }
}