Quick Answer for Busy Parents
St. Mark’s School of Texas runs three separate assessment tracks depending on entry grade. Grade 1 applicants take CATS and ATS. Grades 2 through 4 take the ISEE Primary, with grade 4 adding CATS. Grades 5 through 11 take the standard ISEE and must also complete an interview, while younger boys complete an on-campus observation instead. Deadlines differ by band, ranging from November 9, 2026 to January 8, 2027 for the application form. Decisions arrive March 12, 2027.
Three Testing Tracks, One School
Most independent schools settle on one entrance exam and apply it across the board. St. Mark’s does not, and the reason is developmental rather than bureaucratic. A six-year-old and a sixteen-year-old cannot be measured the same way, so the School uses instruments matched to each stage.
| Entry grade | Assessment required | In place of an interview |
| Grade 1 | CATS cognitive ability assessment and ATS achievement assessment | On-campus student observation |
| Grades 2-3 | ISEE Primary | On-campus student observation |
| Grade 4 | CATS assessment and ISEE Primary | On-campus student observation |
| Grades 5-8 | Standard ISEE, in person or online at home | Interview required |
| Grades 9-11 | Standard ISEE, in person or online at home | Interview required |
St. Mark’s ISEE school code is 441805, and parents register directly with the provider rather than through the School. One detail carries real consequences: the School states that performance is evaluated relative to other students within a narrow chronological age band, so delaying the test to gain preparation time does not improve a score. Sustained ISEE preparation across months beats an intensive December push, and pacing practice matters as much as content review for boys who know the material but run out of time.
What Changes at Grade 5
Grade 5 is the dividing line in the St. Mark’s process. Below it, the School observes boys on campus in a setting designed to see how they engage without the pressure of formal conversation. From grade 5 upward, an interview becomes a required component, and the format itself is unusual: candidates talk with peers as well as with a faculty member. This is closer to being dropped into a conversation among boys than to a one-on-one admissions meeting.
Families choose among an on-campus afternoon interview, a shadow school visit that concludes with the interview, or a virtual interview. The School states there is no preferred method, though it encourages in-person interviews for families inside the Dallas-Fort Worth metroplex. Shadow visits carry a second benefit: your son spends a day inside the actual school day, which is the most reliable fit test available before a decision arrives.
The written components change too. Grades 5 and up submit a Parent Response, a Student Response, and a Student Activities Form. Teacher evaluations become subject-specific, requiring current mathematics and English teachers rather than any teacher a family prefers. Boys who have coasted in one of those two subjects cannot route around it. Our interview preparation focuses on helping a boy talk about genuine interests rather than perform a rehearsed answer, which is what the peer format tends to expose.
Which Track Applies to Your Son?
We will map the exact requirements for his entry grade and build a realistic preparation timeline.
Deadlines That Do Not Line Up
The single most common scheduling error is assuming one family deadline covers two sons applying to different divisions. It does not. Grades 2 through 4 finish their supporting materials in mid-December, six weeks before the upper grades even submit their application forms.
| Grade band | Application form due | Supporting materials due |
| Grades 2-3 | November 9, 2026 | December 14, 2026 |
| Grade 4 | November 9, 2026 | December 14, 2026 |
| Grade 1 | December 14, 2026 | January 29, 2027 |
| Grades 5-8 | January 8, 2027 | January 29, 2027 |
| Grades 9-11 | January 8, 2027 | January 29, 2027 |
Note the inversion: grade 1 applicants submit their form a month after grades 2 through 4 do, but finish everything else six weeks later. A family applying with a first grader and a fifth grader in the same year is managing two different calendars with only one overlapping date.
Where Families Most Often Go Wrong
Registering for the wrong assessment
The ISEE and the ISEE Primary are different exams. A grade 4 family who registers for the standard ISEE has bought the wrong test and may discover it too late to rebook.
Testing in January
The testing service warns that slots grow scarce as the season progresses, and that winter weather, illness, and holiday travel interfere with appointments. A January booking leaves no margin for any of those.
Over-coaching the interview
The peer-inclusive format rewards boys who sound like themselves. A polished answer delivered to a room that includes other fourteen-year-olds tends to land badly.
Writing the Parent Response for the committee
Families often produce a flawless portrait that reads like every other flawless portrait. Specificity, including about where a boy struggles, is more persuasive. Our parent statement guidance and our list of common private school application mistakes both go deeper on this.
Where to Start
Confirm the assessment track for your son’s entry grade, then work backwards from the score-report deadline rather than the application deadline. That single reframing prevents most of the timing problems described above. If you are still deciding when to begin, our guide on timing the private school admissions process sets out a sensible runway.
Build the Timeline Before the Portal Opens
Tell us his grade and where he stands, and we will map the year.
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