Is it mandatory to pass VLK for a teacher who...?

Yes, you must pass the VLK.

If you are not yet 60 years old, then you are conscripted. And the VLK is a mandatory procedure for conscripts. Yes, according to Article 23 of the Law on Mobilization Training and Mobilization, you are not subject to conscription for military service during mobilization, for a special period, as you are to and meet the requirements of the paragraph of this article: "scientific and scientific-pedagogical employees of institutions of higher and professional pre-higher education, scientific institutions and organizations that have an academic title and/or a scientific degree, and pedagogical employees of institutions of professional (vocational-technical) education, institutions of general secondary education, provided that they work, respectively, in institutions of higher or professional pre-tertiary education, scientific institutions and organizations, institutions of professional (vocational-technical) or general secondary education at the main place of work at a rate of at least 0.75". Therefore, you need to write an application for granting interest and supporting documents. And regardless of whether you are fit for military service or not, you must be granted a deferment from military service on the basis of Article 23.