I would be cross if someone was late into my class 2 weeks before a show unless a dire emergency had occurred. Yes you were doing the teacher a favour, but could have gone somewhere with quicker food service than Nandos if you didn't have much time left! Being late in is disruptive to the rehearsal and they likely missed a warm up. (teacher may not be covered on their insurance if your child sustains an injury and hasn't participated in a warm up as part of the class). However, I would have expected two 16 year olds to be able to warm themselves up and would have sent them to the back of the studio or out into the hallway to warm up before returning to class. I recently turned a younger child (and parent) away from class who was 15 mins late to Acro, because she missed the warm up. (however I forwarded her class fee for that session onto another class). It just wasn't worth the risk of an injury and not fair on the other students to have to repeat the warm up.
This kind of attitude is why I try hard not to ask favours of dance parents unless I really have to- I would rather sit up sewing until 2 or 3am many nights in a row than ask for help (which I often do, close to a performance). I usually put a sign up before a show asking if anyone would like to help out with costumes, and if anyone volunteers and requests a sewing job I will happily delegate something, but I never request it of anyone.
Just to ask arethreanyleftatall - how do you know that your dds dance teacher is making a mint? Do you have detailed information on how much the teacher pays each week/month for her venue/hall hire? Insurance, annual teaching membership (many teachers belong to more than one teaching society), PRS, PPL, shoes (often several pairs a year), teaching materials (books, music etc) CPD courses (most dance teachers with recognised societies have to complete several hours of CPD - Continued Professional Development each year to maintain their membership status)- these are are all additional costs. Just like a self employed childminder, first aid and safeguarding courses have to be paid for and attended, and a DBS every 3 years, not to mention the endless extra bits and bobs such as stationery etc that is all part and parcel of the outgoings of a small business. The 'mint' often has to be stretched over 13-15 weeks of school holidays, as many dance schools are termtime only. It may be that your dds teacher is very good at running her business, and does make a good profit, but for many dance teachers it is not the lucrative business that it possibly appears on the surface, and there are many additional outgoings and overheads. I am sure that many dance teachers would be happy to pay all of their volunteers - but just like any other business, these costs would have to be passed back on to the customers, so lessons, costumes, dancewear and exams would therefore cost more.