In my opinion, your newest concern is nothing to lose sleep over. The ability to deliver solutions within the requested parameters is invaluable. There is nothing to prevent your DS from solving problems using algebra as well even if his teacher doesn't want to take the time to discuss that with him. In my experience, it may sometimes be more challenging and thought provoking to use less sophisticated tools to reach a solution. I occasionally challenge my children to provide solutions using different approaches as a way to reach deeper understanding and teach perspective.
Your greater concern is that your DS needs acceleration. You appeared to have partially met that need by the independent Algebra I study. If the issue is that your DS needs that acceleration during school hours, then you need to move up the chain. If the decision is political in the sense that acceleration is forbidden to one and all, then you may be without recourse unless the district is somehow violating statutes or rules. If the decision is political in the sense that they are discriminating against only your DS despite his meeting of all criteria, then try to gather up information regarding other accelerated students (particularly if they appear less qualified criteria-wise) and move up the chain of command.
