I had perfectly joined up handwriting by that same age. They should've let your son continue to use his perfectly legibly print but that doesn't mean that calligraphy is necessarily unreadable, just that your son was bad at it.
I’ve seen tons of others that are simpler, closer to print writing, and much easier to read (fewer extra loops and hoops on letters, crap like that) and I wish they’d taught us one of those, if they had to teach us cursive.
In Britain it's much less fancy [1]. It's also normal to use a fountain pen from around age 7 — at least, I did in the 1990s, and they're still widely sold in shops. These examples seem to be pencil and a rollerball pen though.
(For more images, search "joined up writing primary school" as young children don't often use the word "cursive".)
[1] https://skidbyprimaryschool.org.uk/curriculum-intent/english... (Year 1 = age 5-6, Year 6 = age 10-11).