Educational Studies Program
MIT ESP (Educational Studies Program) runs several programs:
Summer HSSP is a 7-week academic program on weekends for rising 7 - 9th graders. All classes are held at MIT and the cost is $40, with financial aid available.
You can learn more about HSSP here: https://esp.mit.edu/learn/HSSP/index.html
Junction is ESP's most intense program, which offers college-level academic programs during the summer, four nights a week, to advanced 10-12th graders (though 9th graders and graduating seniors can apply as well). The classes are held at MIT; the cost is $600, which includes dinner three nights a week.
You can learn more about Junction here: https://esp.mit.edu/learn/Junction/index.html