Is it permissible to delay the call to prayer (adhan) until the end of a religious lesson, and then immediately make the adhan and the call to commence prayer (iqamah)?

The first is to perform the adhan at the beginning of the time, as Bilal (may Allah be pleased with him) consistently did so. It is permissible to delay it until just before the end of the prayer's time if there is a need, and it does not cause confusion for the listeners. Al-Ansari said in Asna al-Matalib: "So, the adhan for the prayer is given when the time enters, and it is prescribed for it until its time exits." Al-Ruhaibani said in Matalib Uli al-Nuha: "And the adhan at the beginning of the time is sunnah so that the one in a hurry may pray, and its apparent meaning is that it is permissible absolutely as long as the time remains." It is preferable to interrupt the lesson to perform the adhan.