School.cs

using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Umbraco.Core;
using Umbraco.Core.Services;
using Umbraco.Web;

namespace Project.Models
{
    public class School
    {
        private JToken _self;

        public School(JToken self)
        {
            _self = self;
        }

        public int Id
        {
            get
            {
                return (int)_self["school"];
            }
        }

        private string _Name;

        public string Name
        {
            get
            {
                if (_Name == null)
                    _Name = UmbracoContext.Current.ContentCache.GetById(Id).Name;
                return _Name;
            }
        }

        public int Level
        {
            get
            {
                return (int)_self["level"];
            }
        }

        public override string ToString()
        {
            return Name + " " + Level;
        }
    }
}

Schools.cs

using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Collections;
using Mage_Wars_Spellbook_Builder.Helpers;

namespace Project.Models
{
    public class Schools : IEnumerable<School>
    {
        private JArray _self;

        public Schools(JArray self)
        {
            _self = self;
        }

        public new static Schools Parse(string json)
        {
            return new Schools(JArray.Parse(json));
        }

        public IEnumerator<School> GetEnumerator()
        {
            return (_self == null ? new School[] { } : _self.Children().Select(s => s.As<School>())).GetEnumerator();
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return (_self == null ? new School[] { } : _self.Children().Select(s => s.As<School>())).GetEnumerator();
        }

        public bool HasSchool(string school)
        {
            return this.Where(s => s.Name == school).Count() > 0;
        }
    }
}

SchoolsPropertyConverter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Core.PropertyEditors;

namespace Project.Models.PropertyConverters
{
    [PropertyValueType(typeof(Schools))]
    [PropertyValueCache(PropertyCacheValue.All, PropertyCacheLevel.Content)]
    public class SchoolsPropertyConverter : PropertyValueConverterBase
    {
        private readonly string PropertyEditorAlias = "NestedDataType";
        private readonly int[] DataTypeId = { 1096 };

        public override bool IsConverter(PublishedPropertyType propertyType)
        {
            return propertyType.PropertyEditorAlias.Equals(PropertyEditorAlias) && DataTypeId.Contains(propertyType.DataTypeId);
        }

        public override object ConvertSourceToObject(PublishedPropertyType propertyType, object source, bool preview)
        {
            if (source == null)
            {
                return null;
            }

            try
            {
                return Schools.Parse((string)source);
            }
            catch
            {
                return null;
            }

        }
    }
}