For schools using RDP RemoteApps, you need to ensure your RDS server has an active SSL certificate. Steps below to install an SSL certificate for RemoteApps;
1 - Purchase SSL certificate for domain ( e.g. remote.lancaster.leicester.sch.uk)
2 - Download the certificate from website purchased from (Download as IIS)
3 - Follow steps in guide below attached - https://uk.godaddy.com/help/manually-install-an-ssl-certificate-on-my-iis-7-server-4801