[TestClass]
public class GenerarBoletinDeClase
{
    public TestContext TestContext { get; set; }

    public static int Colegio { get; set; }

    [ClassInitialize]
    public static void ClassInitialize(TestContext testContext)
    {
        Colegio = int.Parse(testContext.Properties["colegio"].ToString()); // colegio is equal 7 in here
    }

    [TestInitialize]
    public void TestInitialize()
    {
        int tempColegio = int.Parse(this.TestContext.Properties["colegio"].ToString()); // colegio is equal 7 in here
    }

    [TestMethod]
    public void TestMethod1()
    {
        int colegio = int.Parse(this.TestContext.Properties["colegio"].ToString()); // colegio is equal 7 in here as well

        Assert.AreEqual(7, Colegio);
        Assert.AreEqual(7, colegio);
        Assert.AreEqual(colegio, Colegio);
    }
}

public class TestBase
{
    public TestContext TestContext { get; set; }

    public static int Colegio { get; set; }

    [AssemblyInitialize]
    public static void ClassInitialize(TestContext TestContext)
    {
        Colegio = int.Parse(TestContext.Properties["colegio"].ToString()); // colegio is equal 7 in here
    }

    public TestBase()
    {
        SeleniumHelper = new HelperSelenium(Colegio, WebDriverSelector.ObtenerWebDriver());
        DiccionarioCompartido = new Dictionary<string, string>();
    }