Javascript :
$(document).ready(function() {
$(".hidden").hide();
$("input[type=radio][name=ClassLevel]").change(function() {
var parent_id = $(this).closest("fieldset").attr("id");
var child = $(this).val();
$("#"+parent_id+" .hidden:visible").toggle();
$("#"+parent_id+" ."+child).toggle();
});
});
And the html I used (removed id of each select and added another class that is the same value of the radio button (ie for Certification radio the class of the select associated with it will be certification (added after hidden))
Also, I saw that you will be having multiple pairs on the same page so I've made use of the id of the fieldset (each fieldset must have a unique id in order for this to work properly)
<fieldset id="tbr__15">
<legend>Registrant Information</legend>
<!--<button id="addReg" class="addReg" value="2">+</button>-->
<div id="fieldcontwrapper">
<!-- Wrapper for Group -->
<div id="fieldcont">
<!-- Group your field -->
<div class="required">
<label for="name" class="label_heading">Registrant Name (first and last)</label>
<input type="text" id="name_1" value="name_1">
<br>
<p class="label_heading">Training Level:</p>
<label for="certification">
<input type="radio" name="ClassLevel" value="certification" id="select-certification" class="select-certification">Certification
<!-- <label id="cert-available-classes" class="hidden" for="cert">Certification Classes Available</label> -->
<select class="copy hidden certification" name="cert">
<option value="">Select a Certification Session</option>
<option value="session1cert">Fort Dodge, IA May 5-9, 2014</option>
<option value="session2cert">North Platte, NE Sept 22-26, 2014</option>
<option value="session3cert">Omaha, NE Oct 13-17, 2014</option>
<option value="session4cert">Waterloo, IA Oct 27-31, 2014</option>
<option value="session5cert">Grand Island, NE Nov 17-21, 2014</option>
</select>
</label>
<!--end label for certification-->
<label for="recertification">
<input type="radio" name="ClassLevel" value="recertification" id="select-recertification" class="select-recertification">Recertification
<!-- <label id="recert-available-classes" class="hidden" for="recert">Recertification Classes Available</label>-->
<select class="copy hidden recertification" name="recert">
<option value="">Select a Recertification Session</option>
<option value="session1recert">Fort Dodge, IA May 8, 2014</option>
<option value="session2recert">North Platte, NE Sept 25, 2014</option>
<option value="session3recert">Omaha, NE Oct 16, 2014</option>
<option value="session4recert">Waterloo, IA Oct 30, 2014</option>
<option value="session5recert">Grand Island, NE Nov 20, 2014</option>
</select>
</label>
<!--end label for recertification-->
</div>
</div>
<!-- #fieldcont -->
</div>
<!-- #fieldcontwrapper -->
<button id="addReg" class="addReg">+</button>
</fieldset>
<!--fieldset#tbr__16-->
<fieldset id="tbr__16" class="tbr_fieldset">
<legend>Registrant Information</legend>
<!--<button id="addReg" class="addReg" value="2">+</button>-->
<div id="fieldcontwrapper">
<!-- Wrapper for Group -->
<div id="fieldcont">
<!-- Group your field -->
<div class="required">
<label for="name" class="label_heading">Registrant Name (first and last)</label>
<input type="text" id="name_1" value="name_1">
<br>
<p class="label_heading">Training Level:</p>
<label for="certification">
<input type="radio" name="ClassLevel" value="certification" id="select-certification" class="select-certification">Certification
<!-- <label id="cert-available-classes" class="hidden" for="cert">Certification Classes Available</label> -->
<select class="copy hidden certification" name="cert">
<option value="">Select a Certification Session</option>
<option value="session1cert">Fort Dodge, IA May 5-9, 2014</option>
<option value="session2cert">North Platte, NE Sept 22-26, 2014</option>
<option value="session3cert">Omaha, NE Oct 13-17, 2014</option>
<option value="session4cert">Waterloo, IA Oct 27-31, 2014</option>
<option value="session5cert">Grand Island, NE Nov 17-21, 2014</option>
</select>
</label>
<!--end label for certification-->
<label for="recertification">
<input type="radio" name="ClassLevel" value="recertification" id="select-recertification" class="select-recertification">Recertification
<!-- <label id="recert-available-classes" class="hidden" for="recert">Recertification Classes Available</label>-->
<select class="copy hidden recertification" name="recert">
<option value="">Select a Recertification Session</option>
<option value="session1recert">Fort Dodge, IA May 8, 2014</option>
<option value="session2recert">North Platte, NE Sept 25, 2014</option>
<option value="session3recert">Omaha, NE Oct 16, 2014</option>
<option value="session4recert">Waterloo, IA Oct 30, 2014</option>
<option value="session5recert">Grand Island, NE Nov 20, 2014</option>
</select>
</label>
<!--end label for recertification-->
</div>
</div>
<!-- #fieldcont -->
</div>
<!-- #Copperfield -->
<button id="addReg" class="addReg">+</button>