This is not possible. If you want to display text inside a rect element you should put them both in a group with the text element coming after the rect element ( so it appears on top ).
<svg xmlns="http://www.w3.org/2000/svg">_x000D_
<g>_x000D_
<rect x="0" y="0" width="100" height="100" fill="red"></rect>_x000D_
<text x="0" y="50" font-family="Verdana" font-size="35" fill="blue">Hello</text>_x000D_
</g>_x000D_
</svg>
_x000D_