You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allpages apcontinue="Georg-Christoph-Lichtenberg-Gesamtschule" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="692" ns="0" title="Bismarck-Gymnasium Genthin" />
      <p pageid="702" ns="0" title="Elisabethenschule" />
      <p pageid="711" ns="0" title="Ernst Reuter Schule Karlsruhe" />
      <p pageid="721" ns="0" title="Europaschule Bornheim" />
      <p pageid="699" ns="0" title="Evangelisch Stiftisches Gymnasium Gütersloh" />
      <p pageid="715" ns="0" title="Franz-Stock-Gymnasium Arnsberg" />
      <p pageid="712" ns="0" title="Freiherr-vom-Stein-Schule Neumünster" />
      <p pageid="690" ns="0" title="GGS Siegtal Hennef" />
      <p pageid="716" ns="0" title="Ganztagsschule Saarbrücken-Bellevue Saarbrücken" />
      <p pageid="696" ns="0" title="Gemeinschaftsschule in der Taus" />
    </allpages>
  </query>
</api>