If the "stuff" we do in the classroom isn't changed by Christ, we can hardly call what we are doing Christian education. Godly role-modelling, God-honoring excellence, and God-worshipping chapel services are vitally important, but if the educational core is not transformed by Christ, we will confirm the impression that He is an optional extra in life—an attractive option, but not essential. "Real life," the things that are important, like instruction, methodology, evaluation, and curriculum don't need Him. It's easy to give the impression that leaving Him out of 90% of the school day is OK, as long as He gets a few moments honorable mention in morning devotions.
Christian education is the process of preparing a person for life in which all elements—purpose, teacher, student, content, methodology, philosophy, objectives, assessment, environment, etc.—are related to Christ and are being transformed by Him. Anywhere He is being revealed as the Creator, Sustainer, Redeemer, and Ruler of His world through the life of His children and through His Word, ministry is being done. Some situations may allow the the instruction to be more overt, but any classroom where a teacher is intentional about representing and revealing Christ by exploring the "what has been made" so that "God's invisible qualities—His eternal power and divine nature" are "clearly seen" (Romans 1:20)—is serving Christ and others.