$re = '/"Lead_Owner_Email__c":"(?<leadOwner>.*?)".*?"School__c":"(?<school>.*?)".*?"Level__c":"(?<level>.*?)"/m';
$str = '{"searchRecords":[{"attributes":{"type":"Lead","url":"/services/data/v43.0/sobjects/Lead/00Q1300001TDlooEAD"},"Id":"00Q1300001TDlooEAD","Lead_Owner_Email__c":"mgq23@drexel.edu","InquiryProgram__r":{"attributes":{"type":"Program__c","url":"/services/data/v43.0/sobjects/Program__c/a03a000000FcFl1AAF"},"School__c":"NH","Level__c":"Graduate"}}]}';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php