Bootstrap Button Radio Group Default Value (Check Attribute) Not Working

Bootstrap Button Radio Group Default Value (Check Attribute) Not Working

After countless hours of research, I'm still dumbfounded on how to get the
checked attribute working for button radio groups for Bootstrap. I'm
trying to default "Excellent."
Even though I know for sure radio inputs are checked and not selected, I
even tried selected and nothing works.
<div class="btn-group" data-toggle="buttons">
<label class="btn btn-default">
<input type="radio" name="inputWalls" id="inputWalls"
value="Excellent" checked>
Excellent </label>
<label class="btn btn-default">
<input type="radio" name="inputWalls" id="inputWalls" value="Good">
Good </label>
<label class="btn btn-default">
<input type="radio" name="inputWalls" id="inputWalls" value="Poor">
Poor </label>
</div>
If clarification is needed, please let me know.