While at University I have been asked (encouraged) to write a number of small works for ensembles. There are multiple reasons for this: ensembles are easier to organize performances therefore easier to get compositions heard (which is incredibly important), small chamber works are easier to see the context and flow of the music (so as a composition tutor you're not having to sort through a huge score to see the progress of the music), and fewer instruments means less actual composition for the student. All of these are valid reasons and worthy of continuing this process of composition education at the university level. However, writing a chamber work is not the same as writing for an orchestra or large ensemble (more than 15 instruments).
When studying to be a writer, whether you want to be a novelist, poet, journalist or other there are a variety of writing classes you can take. Each of these styles requires a very different process when writing for the different genres. While writing poetry might hone the use of compact language usage, unless you're writing an epic poem (not something typically expected in a writing course) you're not going to approach the work the same way you would a novel or an academic article. The process is different. The same is true when composing a solo work verses a chamber piece verses an orchestral suite.
Even if the music is approximately the same duration, there is a different approach to how the music written on the page. Ferneyhough is great example of this. His solo flute works are beyond intensive for a single person to grasp, with as much information for the one instrument as there might be in an entire orchestral work - but the information is entirely focused for one player, one instrument. His string quartets have less information for each individual performer, as the nuances of all the additional information of the solo work would be lost in a chamber work. Large ensemble works are even less intense and detailed in terms of what each person is expected to grasp note for note - while the over all work is in many ways more complex than the solo or chamber pieces.
Unfortunately, there is not a lot of encouragement of large ensemble writing while at the university level. What this means is most composers have to learn this on their own either while studying at university (which is what I'm attempting to do) or afterwords when they have little access to support and guidance. The difficulty is we are not teaching our "youth" to compose for large forces and therefore creating a void in the art form.
Established film composers create stables of young composers to help with the work. Philip Glass comments that his stable does a variety of jobs from orchestration his works to working on their own pieces, which Glass then goes over. This sort of mentoring is wonderful but is very specific to the tasks Glass has on his plate. While it has created composers like Nico Muhly, these stables are not generally available; you have to know someone to be selected.
There are a fair number of orchestral call for scores every year. Which means there are numerous opportunities for young composers to submit their scores. But, if there is not someone guiding them on how to create a quality score - the nuances of what a clean score looks like - the chances of them winning any of these competitions is drastically lowered.
I've heard the comment, "If you want to know how to write a good score look at the examples of the great composers." This is a valid statement, but again, without guidance we are expecting our young composers to know what they are looking for and how to translate that to their own music. Beyond this, access to orchestral scores writing in the last 10 years are difficult at best and can be very expensive to obtain (they aren't available at your local library!). So, while it is possible to learn from what Beethoven, Mahler and Shostakovich have done, what about the masters of today? - Williams, Adams, Glass, Carter???
One problem with writing for large ensembles is getting them performed. This is still problematic for many university programs. A university orchestra has enough work to do just getting ready for their various performances. Even just reading student works takes time - never mind creating all the parts (but this is part of the process a student composer needs to learn). Edinburgh University has an orchestra which accepts student compositions for readings and is a boon for composers in the area. The Lamont School of Music gives their orchestration students a chance to hear a reading of a two minute orchestral work and the orchestra does a student composition call for scores each year. These are two examples I am familiar with in terms of promoting orchestral writing. But even in these environments compositional tutoring focuses on small ensembles rather than large.
What I am suggesting is that orchestral directors consider opening up their ensembles to allowing for more student works; amateur orchestras should consider doing the same. Composition tutors should consider including a large work as part of their "requirements" for student compositions - maybe not every years in the undergraduate years, but certainly one large ensemble work over the four years. Then an in-depth examination as to what works and what doesn't in the large work.
Small works are not the same as large works. We spend a lot of time focused on the small stuff, and not enough on the large stuff - in my humble opinion!