As far as I know it's commonly The One Language taught in primary schools, because it's so phonetic and one can build up a fair vocabulary and range of phrases without running into grammar issues straight off the bat. And I know a lot of high schools offer it as a continuing language option, though mine didn't -- our Offered Asian Language (most schools seem to only offer one) was Japanese. If it'd been offered I would definitely have kept it up, because I really enjoyed Indonesian lessons in primary school.