On a more serious note, many years ago, I had a similar experience to Carol of being told I was flat when playing my recorder with a folk group.

However, since I took up the recorder again about 20 years ago I have not come across this problem. It is rare for a reputable manufacturer to produce an out of tune recorder. What is remarkable, IMO is that plastic recorders costing only a few pounds are reliably in tune. I had experience of a few months ago in a workshop led by Joey Oliver of 422. His expensive Overton Whistle was clearly out of tune above top G, in fact he commented on it, while my recorder was fine at those pitches.

That said, there are some caveats.

The pitch of a recorder, especially of the smaller ones are very sensitive to breath pressure, much more so than modern orchestral woodwind, so it is easy play flat or sharp (more common) simply by varying breath pressure.

Recorders are noticeably flat when cold and need to be warmed up. I usually put mine, head joint first, under my armpit. Wooden instruments take more warming up than plastic ones and dense woods such as Blackwood, longer still.

It is often possible to make adjustments to specific notes by partly opening or closing holes. For this reason notes with open fingerings (top D on the soprano/tenor or top F on the alto) are most difficult in this respect.