I think you can use directly
return vars.isValidScore() == true;
something like:
<sequenceFlow id="_5-_6" sourceRef="_5" targetRef="_6" name="EXCEEDS" >
<conditionExpression xs:type="tFormalExpression" language="http://www.java.com/java" >return (exceeds == true);</conditionExpression>
</sequenceFlow>
Demian