We have some parents who regularly lock themselves out of the Parent Portal.
Please could users been shown a message on a failed login to say how quickly their account could be logged. I've included a screenshot from the TES MyConcern login page where they have a similar message.
I do recognise that this is not a perfect solution and that if a parent tried and failed to login twice, then came back to it the next day, they'd get a fresh login page, but it would lock on a third consecutive failed login, even though the parent might say it was their first attempt.