Today's filters are very sophisticated and up to the task of monitoring the sheer variety of kinds of content on the web. Not only can you block specific sites and filter out sexual and violent content, but you can filter email, video, search results, keywords, RPGs, email, and social media. Safe Eyes is also compatible with the iPhone.
The most important aspect of Internet filtering, though, is you, the parent. It is up to you to define "inappropriate content" for the needs of your child and your household. Don't rely on default settings, because they are likely to fail you and let through content of which you disapprove. They may even block content of which you do approve.
Moreover, how you educate your child will determine how well your child is able to handle it when inappropriate content does slip through (and it will). This is especially important for our Aspies. Keeping them sheltered from things they can't handle is important, but making sure they learn how to handle those things is even more vital.