Well, yes, if you’re 12. Which is what the Texas issue was all about.
The need for effectiveness of the vaccine is not “when” you are sexually active, but rather the six month long, three dose period completed “before” you are sexually active.
The whole point is giving it to children before they have their first sexual contact which, like it or not (and I definitely do not), happens as early as 12-14 for a sizable population of young people.