There are lots of projects in the immersion classes— read a book and do a project; research something and make an oral presentation; memorize something and recite it in class; etc. My kids have/had a reasonable but non-zero amount of homework at Gunston. There is often math homework that isn’t class work— it’s assigned at the end of class to be done at home. And studying for tests— how much is necessary depends on the kid. There is a reading log in English, plus Newselas (read an article and answer questions).
For my kids, the accountability for reading in Spanish came in the form of projects related to them and the teacher meeting with each kid to make sure they are reading and understanding their book (but each kid chooses their own book, at least in 6th grade).