Run Multiple test classes using testNG.xml with different priority

I am trying to run multiple test classes using testNG .xml file Class A '''

@Test( priority = 1 )
public void testA1() {
    System.out.println("testA1");
}

@Test( priority = 2 )
public void testA2() {
    System.out.println("testA2");
}

@Test( priority = 3 )
public void testA3() {
    System.out.println("testA3");
}

Class B '''

@Test( priority = 1 )
public void testA1() {
    System.out.println("testA1");
}

@Test( priority = 2 )
public void testA2() {
    System.out.println("testA2");
}

@Test( priority = 3 )
public void testA3() {
    System.out.println("testA3");
}

Output : It should execute Class A with test set priority 1, 2 and 3 Then It should execute Class B with the same Priority 1, 2 and 3

TestNG.XML '''

<suite name="REGRESSION_TEST_SET" thread-count="1" parallel="tests" >
    <test  name="AUTOMATION" group-by-instances="true">

        <classes>

            <class name="ClassA" />
            <class name="ClassB" />
            

        </classes>

    </test>

</suite>