Question:

In our college, salah is performed in congregation which is led by an Imam. Those who are unable to join this congregation, perform salah in a separate congregation of their own. There are around four or five such congregations. Is it correct to repeatedly have such congregations of salah?

Answer: حامدا ومصليا ومسلما

If the area of your college in which the congregational prayer is performed is an official Masjid, then it would be makrooh tahrimi (highly reprehensible) for those people to perform salah in jamat who come after the congregation of the Imam has been completed.

It is stated in Durrul Mukhtaar:

ويكره تكرار الجماعة الخ

Allamah Shaami (عليه الرحمة) writes:

 (1/408 قوله : (ويكره) اي تحريما (شامي

If the area is not an official masjid, rather it was simply designated for performing salah and the intention of an official masjid was not made, then in such a scenario, it would be correct for those who come after to perform salah in congregation.

 
And Allah Ta’aalaa knows best.
Hazrat Mufti Ahmad Khanpuri Saheb (May Allah preserve him)
Mahmoodul Fataawaa 1/450-51