Hi there, sorry for the delay in getting back to you.
We use our custom wordpress site, which admins around the school collate and our comms manager checks before being sent out. We send out the email via Mailchimp which gives great analytics on how many open, what time and what users are clicking on.
We back that up with google analytics to advise on data trends and also online software called hotjar which tracks users movements on the page in desktop, mobile and tablet formats.
All in all, it’s been very successful and once developed, at almost zero cost going from month to month.
Let me know if anyone is after more information.