How to change placement for label of a polygon in mapserver with SLD

I want to change the placement of the label of special polygon by sending SLD to WMS of Mapserver. But it seems as it has no effect. Is label placement in polygons support by mapserver?

        <TextSymbolizer>
        <Font>
            <CssParameter name="font-family">arial</CssParameter>
            <CssParameter name="font-size">20</CssParameter>
        </Font>
        <LabelPlacement>
            <PointPlacement>
                <AnchorPoint>
                    <AnchorPointX>0</AnchorPointX>
                    <AnchorPointY>0</AnchorPointY>
                </AnchorPoint>
                <Displacement>
                  <DisplacementX>0</DisplacementX>
                  <DisplacementY>50</DisplacementY>
                </Displacement>
            </PointPlacement>
        </LabelPlacement>
        <Fill>
            <CssParameter name="fill">#000000</CssParameter>
        </Fill>
    </TextSymbolizer>

<TextSymbolizer>
    <Label>
        <PropertyName>name</PropertyName>
    </Label>
    <Font>
        <CssParameter name="font-family">arial</CssParameter>
        <CssParameter name="font-size">20</CssParameter>
    </Font>
    <LabelPlacement>
        <PointPlacement>
            <AnchorPoint>
                <AnchorPointX>0.5</AnchorPointX>
                <AnchorPointY>0.5</AnchorPointY>
            </AnchorPoint>
            <Displacement>
                <DisplacementX>0</DisplacementX>
                <DisplacementY>50</DisplacementY>
            </Displacement>
        </PointPlacement>
    </LabelPlacement>
    <Fill>
        <CssParameter name="fill">#000000</CssParameter>
    </Fill>
</TextSymbolizer>