At our school, brass and windwood lessons are subsidised by the county council - £40 a term. These are provided by visiting music teachers who go into different schools in the area.
Lessons are usually 20-30 minutes once a week, and often shared between 2-3 pupils learning the same instrument and at a similar level. However, my son was the only person in the school learning sax so he got one-to-one lessons.
Instruments are either bought by parents or some are availabe to borrow from the county music service - free but limited number. We bought ours, using the VAT-free scheme. Got a really could deal because we sourced the best deal on the internet, gave the school the order form and they did the rest, so we only paid the VAT-free price.
Some parents rent from a local music shop, after 3 months you can either hand it back, keep on renting or buy the instrument with the 3 months rental deducted.
Every child in Yrs 2-4 now learns recorder once a week, in whole-class situations. Each child was given a recorder and book for free, I think it's some new government scheme. Children in Yrs 5-6 who didn't qualify for these are offered recorded club once lunchtime, but have to provide own recorder and book.
While school music lessons are probably less effective than 'proper' one-to-one lessons elsewhere, it does give a relatively cheap introduction to an instrument. My older two are now paying £120 a term each for lessons at secondary school, and while their teacher is superb, the financial aspect is a huge shock to the system, and at that point it really does raise questions about equal opportunities.
If the PTA is trying to fund music for as many as possible, I would try to focus on recorders first. I know it's not the coolest instrument, but it really is a 'proper' instrument and can give great grounding for further development.