Complex sentence: However, Oriyas were severely disadvantaged by having to attend Presidency College in Kolkata for B.A. degrees, until the collegiate branch of Zilla school was converted into a full Bachelor's degree granting college under the commissioner, T. E. Ravenshaw.
Split into simpler sentences: However, Oriyas were severely disadvantaged by having to attend Presidency College in Kolkata for B.A. degrees. This was until the collegiate branch of Zilla school was converted into a full Bachelor's degree granting college under the then commissioner, T. E. Ravenshaw.