diff --git a/apps/web/src/oj/class/pk.vue b/apps/web/src/oj/class/pk.vue
index f1e0cf0..a3b08c2 100644
--- a/apps/web/src/oj/class/pk.vue
+++ b/apps/web/src/oj/class/pk.vue
@@ -4,7 +4,7 @@ import { MdPreview } from "md-editor-v3"
 import "md-editor-v3/lib/preview.css"
 import { useThemeVars } from "naive-ui"
 import { getClassBattle, getClassPk } from "oj/api"
-import { classLabel } from "oj/submission/utils"
+import { classLabel, groupClassOptions } from "oj/submission/utils"
 import { useAIStream } from "shared/composables/aiStream"
 import { useBreakpoints } from "shared/composables/breakpoints"
 import { useUserStore } from "shared/store/user"
@@ -102,25 +102,13 @@ function setPeriod(value: ClassPkPeriod) {
 }
 
 /** 「+ 加一个班」：这学期在用的班（班级对抗里有的），按年级分组，自己年级放最前 */
-const addOptions = computed(() => {
-  const grade = selected.value[0]?.slice(0, 2)
-  const groups = new Map<string, { label: string; value: string }[]>()
-  for (const item of battle.value) {
-    if (selected.value.includes(item.className)) continue
-    const key = item.className.slice(0, 2)
-    const list = groups.get(key) ?? []
-    list.push({ label: classLabel(item.className), value: item.className })
-    groups.set(key, list)
-  }
-  return [...groups]
-    .sort((a, b) => (a[0] === grade ? -1 : b[0] === grade ? 1 : b[0].localeCompare(a[0])))
-    .map(([key, children]) => ({
-      type: "group" as const,
-      label: `${key} 级`,
-      key,
-      children: children.sort((a, b) => a.value.localeCompare(b.value, "zh", { numeric: true })),
-    }))
-})
+const addOptions = computed(() =>
+  groupClassOptions(
+    battle.value.map((item) => item.className).filter((name) => !selected.value.includes(name)),
+    undefined,
+    selected.value[0]?.slice(0, 2),
+  ),
+)
 
 const mode = computed(() => {
   if (!pk.value || pk.value.classes.length < 2) return "empty"
diff --git a/apps/web/src/oj/classroom/board.vue b/apps/web/src/oj/classroom/board.vue
index 8a94636..f63e93e 100644
--- a/apps/web/src/oj/classroom/board.vue
+++ b/apps/web/src/oj/classroom/board.vue
@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { getClassBoard, setClassLesson } from "oj/api"
+import { groupClassOptions } from "oj/submission/utils"
 import UserName from "shared/components/UserName.vue"
 import { useLeaveStudents } from "shared/composables/leaveStudents"
 import { useCollabStore } from "shared/store/collab"
@@ -49,17 +50,9 @@ const languageOptions = LESSON_LANGUAGES.map((value) => ({
 }))
 const saving = ref(false)
 
-function classLabel(name: string) {
-  return /^\d{3,}$/.test(name) ? `${name.slice(0, 2)}计算机${name.slice(2)}班` : name
-}
-
 const classOptions = computed(() => {
   const list = configStore.config?.classList ?? []
-  const names =
-    board.value?.className && !list.includes(board.value.className)
-      ? [board.value.className, ...list]
-      : list
-  return names.map((name) => ({ label: classLabel(name), value: name }))
+  return groupClassOptions(board.value?.className ? [board.value.className, ...list] : list)
 })
 
 async function load() {
diff --git a/apps/web/src/oj/problemset/components/ClassView.vue b/apps/web/src/oj/problemset/components/ClassView.vue
index 8443700..e1feeff 100644
--- a/apps/web/src/oj/problemset/components/ClassView.vue
+++ b/apps/web/src/oj/problemset/components/ClassView.vue
@@ -2,6 +2,7 @@
 import { useThemeVars } from "naive-ui"
 import { getProblemSetClassView } from "oj/api"
 import { useTone } from "oj/submission/composables/tone"
+import { classLabel, groupClassOptions } from "oj/submission/utils"
 import UserName from "shared/components/UserName.vue"
 import { parseTime } from "utils/functions"
 import type { ProblemSetClassView } from "utils/types"
@@ -35,16 +36,13 @@ watch(className, (value, old) => {
   if (old && value !== data.value?.className) load()
 })
 
-function classLabel(name: string) {
-  return /^\d{3,}$/.test(name) ? `${name.slice(0, 2)}计算机${name.slice(2)}班` : name
-}
-
-const classOptions = computed(() =>
-  (data.value?.classes ?? []).map((item) => ({
-    value: item.className,
-    label: `${classLabel(item.className)}（${item.joined}/${item.size} 人加入）`,
-  })),
-)
+const classOptions = computed(() => {
+  const classes = new Map((data.value?.classes ?? []).map((item) => [item.className, item]))
+  return groupClassOptions([...classes.keys()], (name) => {
+    const item = classes.get(name)!
+    return { value: name, label: `${classLabel(name)}（${item.joined}/${item.size} 人加入）` }
+  })
+})
 
 const joined = computed(() => data.value?.students.filter((s) => s.joinTime) ?? [])
 const absent = computed(() => data.value?.students.filter((s) => !s.joinTime) ?? [])
diff --git a/apps/web/src/oj/rank/list.vue b/apps/web/src/oj/rank/list.vue
index b7881aa..e5cbbce 100644
--- a/apps/web/src/oj/rank/list.vue
+++ b/apps/web/src/oj/rank/list.vue
@@ -9,7 +9,7 @@ import type {
 } from "@oj2/contract"
 import { useThemeVars } from "naive-ui"
 import { clearMood, getClassBattle, getRankBoard, getWeeklyChampions, setRankHidden } from "oj/api"
-import { classLabel } from "oj/submission/utils"
+import { classLabel, groupClassOptions } from "oj/submission/utils"
 import UserName from "shared/components/UserName.vue"
 import { useBreakpoints } from "shared/composables/breakpoints"
 import { useConfigStore } from "shared/store/config"
@@ -261,12 +261,8 @@ const minis = computed<MiniRank[]>(() => {
 
 const teacherClassOptions = computed(() => {
   const list = configStore.config?.classList ?? []
-  const all =
-    teacherClass.value && !list.includes(teacherClass.value) ? [teacherClass.value, ...list] : list
-  return [
-    { label: "全部", value: "" },
-    ...all.map((name) => ({ label: classLabel(name), value: name })),
-  ]
+  const all = teacherClass.value ? [teacherClass.value, ...list] : list
+  return [{ label: "全部", value: "" }, ...groupClassOptions(all)]
 })
 
 const myBattle = computed(() => battle.value.find((item) => item.className === classContext.value))
diff --git a/apps/web/src/oj/submission/utils.ts b/apps/web/src/oj/submission/utils.ts
index e018c8b..7f9ce0d 100644
--- a/apps/web/src/oj/submission/utils.ts
+++ b/apps/web/src/oj/submission/utils.ts
@@ -40,14 +40,50 @@ export function submissionDayText(time: string) {
  */
 export function classLabel(className: string | null) {
   if (className === null || className === NO_CLASS) return "没填班级"
+  if (!/^\d{3,}$/.test(className)) return className
   return `${className.slice(0, 2)}计算机${className.slice(2)}班`
 }
 
+type ClassOption = { label: string; value: string }
+
 /**
- * 班级下拉的选项：配置里的班，最后一项「没填班级」（这批号也要能和普通班一样圈出来看）。
- * 带进来的班不在配置里（老班、手打的）也要显示得出来，不然框里是空的却在筛
+ * 全站的班级下拉都按年级分组：「25 级」底下列 251、252……，新的年级在上，组里按班号排
+ * （11 班排在 2 班后面）。年级是班号前两位，和排名的「本年级」同一个口径。
+ * `first` 给了就把那个年级提到最前（班级 PK 加班时先给同年级的）。
+ * `toOption` 换掉选项长相（题单的「n/m 人加入」、登录框的 ks 前缀）；不是数字班号的
+ * 名字不分组，按原顺序跟在最后。
+ */
+export function groupClassOptions<T extends ClassOption = ClassOption>(
+  names: string[],
+  toOption: (name: string) => T = (name) => ({ label: classLabel(name), value: name }) as T,
+  first?: string,
+) {
+  const groups = new Map<string, string[]>()
+  const rest: string[] = []
+  for (const name of new Set(names)) {
+    if (!/^\d{3,}$/.test(name)) {
+      rest.push(name)
+      continue
+    }
+    const grade = name.slice(0, 2)
+    groups.set(grade, [...(groups.get(grade) ?? []), name])
+  }
+  const grouped = [...groups]
+    .sort((a, b) => (a[0] === first ? -1 : b[0] === first ? 1 : b[0].localeCompare(a[0])))
+    .map(([grade, list]) => ({
+      type: "group" as const,
+      label: `${grade} 级`,
+      key: `grade-${grade}`,
+      children: list.sort((a, b) => a.localeCompare(b, "zh", { numeric: true })).map(toOption),
+    }))
+  return [...grouped, ...rest.map(toOption)]
+}
+
+/**
+ * 班级下拉的选项：配置里的班按年级分组，最后一项「没填班级」（这批号也要能和普通班一样
+ * 圈出来看）。带进来的班不在配置里（老班、手打的）也要显示得出来，不然框里是空的却在筛
  */
 export function classSelectOptions(list: string[], current: string) {
-  const all = current && current !== NO_CLASS && !list.includes(current) ? [current, ...list] : list
-  return [...all, NO_CLASS].map((item) => ({ label: classLabel(item), value: item }))
+  const all = current && current !== NO_CLASS ? [current, ...list] : list
+  return [...groupClassOptions(all), { label: classLabel(NO_CLASS), value: NO_CLASS }]
 }
diff --git a/apps/web/src/shared/components/Login.vue b/apps/web/src/shared/components/Login.vue
index 243072e..a194684 100644
--- a/apps/web/src/shared/components/Login.vue
+++ b/apps/web/src/shared/components/Login.vue
@@ -1,4 +1,5 @@
 <script setup lang="ts">
+import { classLabel, groupClassOptions } from "oj/submission/utils"
 import { errorCode } from "utils/api"
 import { STORAGE_KEY } from "utils/constants"
 import storage from "utils/storage"
@@ -52,14 +53,13 @@ function filterClassUser(pattern: string, option: SelectOption) {
 // 空串是「没有我所在的班级」，null 才是没选 —— 往届的班级毕业后会从后台配置里删掉，
 // 这一项是他们唯一的入口，写完整用户名登录
 const OTHER_CLASS = ""
-const classList = computed<SelectOption[]>(() => {
-  const configs =
-    configStore.config?.classList.map((item) => ({
-      label: `${item.slice(0, 2)}计算机${item.slice(2)}班`,
-      value: `ks${item}`,
-    })) ?? []
-  return [...configs, { label: "没有我所在的班级", value: OTHER_CLASS }]
-})
+const classList = computed<SelectOption[]>(() => [
+  ...groupClassOptions(configStore.config?.classList ?? [], (item) => ({
+    label: classLabel(item),
+    value: `ks${item}`,
+  })),
+  { label: "没有我所在的班级", value: OTHER_CLASS },
+])
 // 选了具体班级就是「选姓名」，选了「没有我所在的班级」就是「写用户名」
 const isClassLogin = computed(() => Boolean(form.value.class))
 const passwordRule: FormItemRule[] = [
@@ -190,7 +190,8 @@ function onUsernamePicked() {
 function restoreLastClass() {
   if (form.value.class !== null) return
   const last = storage.get(STORAGE_KEY.LOGIN_CLASS)
-  if (typeof last === "string" && classList.value.some((item) => item.value === last)) {
+  const known = (configStore.config?.classList ?? []).map((item) => `ks${item}`)
+  if (typeof last === "string" && known.includes(last)) {
     form.value.class = last
   }
 }