Grid Field in a Channel Form

I’m trying to create a channel form with a grid field that contains a text field and 3 relationship fields. I’m using a tag pair for the grid field, but if there’s anything in the tag pair, I get a PHP error:

Fatal error: Cannot use object of type EllisLab\ExpressionEngine\Model\Channel\ChannelEntry as array in …ee/legacy/libraries/Grid_parser.php on line 144

I get the error even if there’s a carriage return in the tag pair. Test code is below. Any help is greatly appreciated.

{exp:channel:form channel="summer_registration" id="camp_form" class="standard"}
<label>Email:</label>{field:email_address}   <!-- this works -->


<label>Student Name:</label>
{summer_camps}{summer_camps:student_name}{/summer_camps} <!-- anything inside this tag throws error -->


{/exp:channel:form}