Hi everyone, thought I would chime in on this topic since I have come to research quite a bit about clerical/mass attire/vestments, etc. I am a fourth year diaconate student who is having to deal with this now that my brothers and I are serving at Mass.
The first and best place to go with a question about what is allowed/used in Mass is the GIRM (General Instruction of the Roman Missal) which contains the rubrics for what is to be done in Mass.
As for vestments, ironically, it says that the preferred vestment for ministers of any rank (this includes lectors and young altar servers) is the alb. Forgive me for not quoting the exact GIRM number but I was just reading it last night. Cassock and surplice may be used as well according to local custom so don’t go throwing out all the cassocks just yet!
At our small parish, our servers use a black cassock and white surplice, even the girls. When I began serving earlier this year, I bought a cassock to fit me better and used a surplice from the church. However, our diaconate director just issued a notice to us that our bishop wants us specifically wearing the alb if not already. We have been duly instituted by the bishop as Acolytes, an official ministry in the church. So, I have ordered an alb. THis is in preparation for our ordination coming in a bit more than a year.
So at our Mass, you have servers who are wearing cassocks/surplices, me in an alb and the priest and deacon wearing their vestments! A little bit of everything…
Also, the GIRM states that the use of a cincture, which is the cloth belt around a person’s waist who is wearing an alb, is to be used if necessary. Some albs are sort of meant to drape and not be cut in half by a cincture, so if that is the case, you are not required to wear a cincture, only out of necessity.
Hope this helps!