I think it's a cute idea, but also keep in mind that mint can really be a scourge if you plant it in the ground (talk about spreading - it's worse than bamboo, or ivy!). I would definitely buy a flower pot and plant the mint in there, so they don't mistakenly plant it in their flower bed and then have it take over their entire yard (I speak from experience, LOL). Then give the mint in the flowerpot to the teacher with a card that explains that it is lemon mint, great for sun tea. (My aunt grows chocolate mint and makes a liqueur that is absolutely to die for - I bet lemon mint would be great for that, too!) One way to make it more personal is to have your child paint the flower pot, maybe put their hand print and name on there. My mom was a teacher for 20 years and she loved those types of gifts.