Unity3d SceneManager

GameObjectExtension.cs

using UnityEngine;

namespace Assets.Scripts
{
    public static class GameObjectExtension
    {
        public static void AddChild(this GameObject parent, GameObject child)
        {
            var instantiatedObject = GameObject.Instantiate(child);
            instantiatedObject.transform.parent = parent.transform;
        }

        public static void RemoveAllChildren(this GameObject parent)
        {
            for (var i = 0; i < parent.transform.childCount; i++) {
                GameObject.Destroy(parent.transform.GetChild(i).gameObject);
            }
        }
    }
}

Scene.cs

using UnityEngine;

namespace Assets.Scripts
{
    public abstract class Scene : MonoBehaviour
    {
    }
}

Scene1.cs

using UnityEngine.UI;
using UniRx;

namespace Assets.Scripts.Scenes
{
    public class Scene1 : Scene
    {
        public Button switchButton;

        void Start()
        {
            switchButton
                .OnClickAsObservable()
                .Subscribe(_ => SceneManager.Change<Scene2>());
        }
    }
}

Scene2.cs

using UnityEngine.UI;
using UniRx;

namespace Assets.Scripts.Scenes
{
    public class Scene2 : Scene
    {
        public Button switchButton;

        void Start()
        {
            switchButton
                .OnClickAsObservable()
                .Subscribe(_ => SceneManager.Change<Scene1>());
        }
    }
}

SceneManager.cs

using UnityEngine;

namespace Assets.Scripts
{
    public static class SceneManager
    {
        private static GameObject getRootGameObject()
        {
            return GameObject.Find("RootGameObject");
        }

        private static void destroyCurrentScene()
        {
            var currentScene = getRootGameObject().GetComponentInChildren<Scene>();
            GameObject.Destroy(currentScene.gameObject);
        }

        public static void Change<T>() where T : Scene
        {
            destroyCurrentScene();
            var prefabPath = string.Format("Scenes/{0}", typeof(T).Name);
            var newSceneObject = Resources.Load<GameObject>(prefabPath);
            getRootGameObject().AddChild(newSceneObject);
        }
    }
}