Here's the statute:

§ 568.045. Endangering the welfare of a child in the first degree, penalties
1. A person commits the crime of endangering the welfare of a child in the first degree if:
(1) The person knowingly acts in a manner that creates a substantial risk to the life, body, or health of a child less than seventeen years old; or
(2) The person knowingly engages in sexual conduct with a person under the age of seventeen years over whom the person is a parent, guardian, or otherwise charged with the care and custody;
(3) The person knowingly encourages, aids or causes a child less than seventeen years of age to engage in any conduct which violates the provisions of chapter 195;
(4) Such person enlists the aid, either through payment or coercion, of a person less than seventeen years of age to unlawfully manufacture, compound, produce, prepare, sell, transport, test or analyze amphetamine or methamphetamine or any of their analogues, or to obtain any material used to manufacture, compound, produce, prepare, test or analyze amphetamine or methamphetamine or any of their analogues; or
(5) Such person, in the presence of a person less than seventeen years of age or in a residence where a person less than seventeen years of age resides, unlawfully manufactures, or attempts to manufacture compounds, possesses, produces, prepares, sells, transports, tests or analyzes amphetamine or methamphetamine or any of their analogues.
2. Endangering the welfare of a child in the first degree is a class C Felony unless the offense is committed as part of a ritual or ceremony, or except on a second or subsequent offense, in which case the crime is a class B felony.
3. This section shall be known as "Hope's Law".

The annotations to the statute state that a charge under Mo. Rev. Stat. § 568.045.1(1) is not in and of itself a sexual offense; thus, when defendant was charged with allowing the victim to be sexually molested, but not acting with the victim's stepfather as a co-conspirator or an accessory, the charges did not fall under the 10-year statute of limitations under Mo. Rev. Stat. § 556.037 and thus were properly dismissed. State v. Rains, 49 S.W.3d 828, 2001 Mo. App. LEXIS 1263 (Mo. Ct. App. 2001).

Thus, as long as he was charged under subsection (1) and not subsection (2), it is not a sexual offense, and he should not be considered a sex offender.