One solution strategy that works very well from my experience is to ask them upfront whether they want to play "for real" or to play to learn. [edit: A third mode is "for (silly) fun" where everything is allowed.] This works for all ages... and for boardgames and physical games. It's their choice which mode they want to play in, and they trust and respect you more when given the choice. You treat them as a peer. You…
An other option is to play cooperative rather than competitive games.
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