How long is a piece of string?
Teachers can leave for all manner of reasons:- relocation, promotion, secondment, maternity leave, unhappy at previous school, just fancied a change of scenery, leaving the profession for a career change, retirement etc. Some years, hardly anyone leaves. Other years, it can feel like quite a lot. It may just be a coincidence, or it may suggest a lot of unhappiness and unrest behind the scenes. The most usual reasons for a massive exodus are a bad Ofsted, or new management coming in with new ideas/ways which don't align with the beliefs of the current staff (or new management who clearly want to bring their own people in, so make working conditions as rubbish as possible for existing staff to encourage them to jump ship). With budgets so shockingly low now, it's sadly not that uncommon for teachers who are on better wages (which reflect their years of experience) to be hounded out so they can be replaced by cheaper ECTs. 😥
Obviously it depends how many you mean when you say 'an influx' are leaving? In a school of that size, even 4 or 5 leaving at the same time may not be that noticeable (unless they're all leaving from the same year groups, so the whole EYFS team, for example, is changing). However, in a small school with only 4 teachers it can make a massive difference to the dynamics if even one leaves, let alone two or more at the same time.
When you say parents are concerned, do you mean simply about the amount of teachers leaving in one hit, or were there concerns before that which are now seemingly being founded by the amount of teachers who now want out?