The school is located on a one-hectare lot on Valenzuela Street (now Jose Gil Street), in the residential hub of San Juan town. It is not named after St. John the Baptist which explains why it is a non-sectarian school. Since it was going to be put up in San Juan and the Marquezes all resided here, they thought that the English name for the town would do, so St. John's was it.

It was in 1930 that the Marquez sisters decided to open a school of their own. Teaching was their profession and the hobby, too, of Concepcion. The idea was backed by their father, the late Gregorio Marquez, who was himself a public school teacher. He gave his daughters the money needed to rent the building and lot that was to become the first St. John's Academy.The building used to be the vacation house for the Recoletos Order. It was on a lot on Pinaglabanan Street near the Old Manila Waterworks reservoir. After some renovations, the school was opened. It offered a complete elementary course, four years of primary and three years of intermediate, and a secondary course with second year as the highest class.

The first faculty members were no other than the seven sisters. Other teachers were hired during the year but most of the English classes from the kindergarten to the high school levels were handled personally by the Marquez sisters. That might have had something to do with the fact that the early St. Johnites could communicate in remarkable English.

The Marquez sisters, particularly Concepcion who stayed longest in the academe, always believed that English is a basic course and that if one knows correct English, he can get by easily in the other subjects. Correct English thus became the top factor in employing teachers for any subject at St. John's. It is also the official language in school until now.

What kind of school is St. John's? It is, and always was, small. Its Class of '34 numbered only five. The present enrollment is only 1,746 pre-school to high school students. It remains small because it has a natural screening scheme in admitting students.

During the second world war, St. John's suffered in the shelling and razing of San Juan. During the Japanese occupation, it reopened in June 1943. Classes were held in Mrs. Concepcion Gil's place located along what is now N. Domingo Street. Grade VI was the highest class. Class '42 who should have graduated in March of that year were given certificates in 1943. It re-opened after the liberation on an old two-storey house sitting on the present site on Valenzuela Street. The first year was the only class in the high school in 1945. This batch became the first graduates after liberation. The house, abandoned during the war, belonged to a sister of Concepcion's husband, the late Civil Service Commissioner Jose Gil, Sr. Adjacent lots were gradually purchased for the expansion to accommodate the growing number of enrollees.

On its 74th year today, the school can take pride in the concrete Jose Gil and Marquez Buildings which are enough to accommodate the students from pre-school to high school. It also has its spacious covered court which is being used as a venue for various school activities.

As what Mrs. Concepcion Marquez-Gil would say: "Our idea of a school was one that we could run the way a school should be run. It wasn't going to be prestigious but a good one."