My teenager has started to have feelings for someone. How do I guide this without rushing him into marriage?

Acknowledge his feelings as something normal, then guide them towards a halal intention without hurrying. Do not tease or shame those feelings, because that will make him keep secrets. Explain that mature love is channelled through marriage when the time and ability come. For now, encourage him to focus on his studies, improve himself, and learn the qualities of a good spouse in terms of religion and character. Teach him to guard his heart and his boundaries while waiting. Pray for him quietly. See educating the family.