The speaker is a teacher who describes the job as a kind of priesthood. Teaching isn't just work for them; it's a calling they have given their life to. But the religion they serve is a troubling one. Children become "gifts" offered up on altars, and those altars are ordinary classroom furniture: desks and shelves. The comparison to sacrifice suggests that students are being handed over to something that may not care for them.
The last line makes the speaker's doubt clear. Chalk boards, white boards and overheads are the tools of the trade, yet the speaker says they "pave the path to hell." The poem seems to suggest that the changing technology of teaching, and perhaps the system behind it, leads nowhere good. The mood is bitter and uneasy. The speaker sounds trapped, devoted to a calling they no longer trust, and the religious language makes that disillusionment feel heavy and almost guilty.