If I put enough time (& money) into my step son, will he experience sharp improvements?

A common path for a high school graduate who is not ready to go to a four year college is to start at a community college, then transfer to a four year college to complete the bachelor’s degree. Remedial course work, if necessary, is readily available at community colleges. It may take more than two years to become transfer-ready, but extra semesters or years at a community college cost less than at a four year college. This does, however, require committing to the transfer pathway, and also requires that you live in a state with good community colleges that offer course work that prepares the student for transfer in the desired major.